The B&W; Zeppelin or The Altec Lansing T612 is something that is definitely not portable.

I think you should try the Logic3's newest i-Station Traveller

http://www.slipperybrick.com/wp-content/uploads/2007/08/logic3-i-station-traveller-iphone.jpg

The system consists of a couple 4-watt, 35mm neodymium driven speakers and a dock that can accommodate the iPhone either vertically or horizontally.

To help make the Traveller more travel friendly the speakers will actually slide together to enclose the docking area and make the whole works only 170mm wide. The device is also compatible with any iPod or any media player that has a standard 3.5mm headphone jack. We’re thinking that the iPhone probably connects through the headphone jack as well.

The iPhone speaker dock is expected to be available soon from Logic3 retailing for around $60.

http://www.logic3.com/_images/products/300/140-1.jpg

Here's a detailed review : --

Design

Logic3's newest i-Station Traveller boasts a sleek, black gloss finish with silver trim, which perfectly complements the iPhone. Measuring just 170mm across, Logic3 has created a stylish and chic system for both home and abroad.

As the first dedicated iPhone speaker system on the market, the i-Station Traveller for iPhone's innovative and compact design accommodates the iPhone both vertically and on its side for optimal use. In fact, with the sleek adjustable holding system, Logic3's latest i-Station can turn your iPhone into an all-singing, all-dancing multimedia system, so you can watch your downloaded videos in style!

Sound

Sound quality is a key feature of the iPhone and Logic3's iPhone speakers have been specifically designed to complement and enhance this sound, with the TDMA noise - the sound emitted from mobile phones and heard through speakers - kept to a minimum.

If you're feeling generous or simply want to show-off, why not share your playlist with the world through the 35mm neodymium drivers? The fantastic sound quality is not compromised by the compact design of the i-Station Traveller for iPhone, which boasts a total output of 4 watts.

http://www.slashphone.com/media/data/800/istation-2.jpg

Compatibility

Still waiting for an iPhone? Fear not - for those retro iPod owners who are yet to upgrade, Logic3's new offering is also compatible with any gadget with a 3.5mm jack, including the whole iPod range, MP3 players and even your PSP. Ticking all the boxes, Logic3 provides a 3.5mm to 2.5mm stereo converter so you can even connect a compatible mobile phone.

Connectivity

Giving you the option to showcase your iPhone on the move, the i-Station Traveller for iPhone comes supplied with four AAA batteries. A mains adaptor also comes as standard - great if you would rather make your iPhone's i-Station a permanent fixture in your house.

Complete with a velvet-finish case, the i-Station Traveller for iPhone will be available for just 29.99 from high street retailers. You will also be able to snap them up online through Amazon and www.logic3.com.

You may also try : --

JBL On Stage IIIP Portable Speaker Dock For IPhone 1G And IPod (Black)

Price: $129.95

http://images.amazon.com/images/G/01/electronics/detail-page/B0016BI0TA-1.jpg

Link to buy-- http://www.amazon.com/JBL-Stage-Portable-Speaker-iPhone/dp/B0017XMN7C

Iphone Speaker (Black) - Portable Speaker with Dock & Remote Control for All Ipod and I-phone Models including iphone 3G (FREE SHIPPING TO USA @ CHECK OUT)

$49.99

http://ecx.images-amazon.com/images/I/41zaYJ2RGPL._SL500_AA280_.jpg

SOME ARTICLES YOU MAY LIKE TO READ----

1. Reviews, comparisons, and write-ups on iPod speaker systems, including home and mobile speakers.

LINK-- http://ipod.about.com/od/speakers/Speakers.htm

The Altec Lansing T612 system is one of the best.
Best feature of the system: It doesn't buzz like other speakers will with GSM phones nearby. Works with both first-gen and 3G iPhones and other iPods.

These are the best iPhone dock with speakers that you can choose from.

1. Klipsch iGroove SXT is petite but powerful iPod and iPhone dock that gives out a very impressive sound quality. The design is sleek but simple and has many features like an S-video output for TV connection, a quick charging circuit to charge your iPhone and it is very portable and lightweigh.

2. Another option is the Altec Lansing Mix iMT800 that is design to appeal someone's peculiar taste but this is very cool. It's like a new age boom box that gives outstanding sound. It has two auxiliary inputs that is place on top of the unit so that it is easily accessible and powered by 8D batteries.

3. iHome iPi has a slim design with transparent face plate and bulging black speakers. It has a line-in jack with good sound quality and GSM shielding for optimum compatibility with the iPhone.

4. Bose SoundDock 10 is very classy, I'm sure your wife is going to love its very elegant and classy look. It has a minimalist design, a composite output/line input, a GSM shielded for iPhone and interchangeable dock.

5. iHOme iHome is always a great choice for it has a built-in clock radio allowing you to wake to your iPod songs or the radio.

6. Another great option is the Yamaha PDX-30 Speaker Dock which is lightweight and gives amazing audio. It has two large front speakers that emit rich sounds and a dynamic bass.

Unfortunately, the M612 is not what I would call "portable" weighing in at 9 lbs with an 8x14" form factor :( i'm not sure if it works on battery either.

The Zeppelin has also been reported to have had problems with the iphone, though it works well for ipods. Its not very rugged or portable either.

Altec Lansing does produce high quality, portable speakers at a range of prices. Some top products include:
Altec Lansing IM702 (~150 on amazon)
http://www.amazon.com/Altec-Lansing-inMotion-IMT702-Speaker/dp/B001K4YWCW/ref=sr_1_30?ie=UTF8&s=electronics&qid=1232002488&sr=8-30

My favorite: IM600 (~100 on amazon) a new version with the same name will be released soon, but with cost about 140. Also supports radio function and super-portable. My friend brings hers with us all the time. It really does have nice sound quality and battery life.
Note that the new version may be worth waiting for, as they have fixed the buzzing problem that occurs when your iphone is getting a call.
http://www.amazon.com/Altec-Lansing-iM600USB-Portable-Receiver/dp/B001IZYV2E/ref=sr_1_5?ie=UTF8&s=electronics&qid=1232002958&sr=1-5

From there the prices and sound quality continue to drop. I would go with altec lansing over other brands, they really dedicate an entire line to apple/iphone products

You should definately check out the Tivoli Audio iSongBook ($199.99). It's small and portable. It can run on AA batteries or can be plugged in. What's great is if you use AA rechargeable batteries the iSongBook will act as a recharger for them. The sound is truely amazing for its size and it plays in true stereo separation as the 2nd speaker is detachable. The dock is very unique. When not in use it folds out of the way. The outer case is weather resistant so it's made for use outdoors as well as in.

The B&W Zeppelin is the best speaker system for the iPhone. The novel "floating" dock that B&W designed allows you to hold the iPhone as if it weren't currently docked. The Zeppelin contains technology that are in B&W speakers at Skywalker Sound and Abbey Road Studios. You're not going to find better sound quality than this in a dock speaker system – and this one is completely shielded so you won't get phone interference. It also includes a nicely sculpted remote control that fits neatly in the palm of your hand.