I got a Proporta one for our camping trip this summer - got 3 charges for an iphone out of it, was impressed. It looks quite nice too.

I have a couple of these and they've been superb, cheap as ****

http://www.amazon.co.uk/Duracell-PPS1-mini-USB-Connectors-Batteries/dp/B001FC49TK

I have a powermonkey set which I use when in London. Quite a bit more expensive, and half as big as those Trents, but versatile. The trents look excellent.

Hmmm, battery wars 😕
this is now leading my 'wish list'
http://www.amazon.co.uk/New-Trent-iCruiser-IMP1000-Blackberry/dp/B004CHMP50/ref=pd_rhf_shvl_3

11000mAh of juice and proper charger, 270g, dimensions: 4.3"x2.5"x0.8

I've got this one from DX:
[url= http://www.dealextreme.com/p/usb-ac-recharged-1w-65lm-luxeon-led-flashlight-and-cell-phone-pda-adapters-1-18650-included-17470 ]Luxeon LED Flashlight and Cell Phone/PDA Adapters[/url]
It uses the same battery as my night riding lights so I usually have spare cells. Torch is actually very good, and a handy thing to have in your pack.

I've got one of these

http://www.portablepowersupplies.co.uk/portapowPremium.htm

Very good and loads of connectors

amazon had a really good deal on a while back as long as you promised to write a review. Was tempted but forgot to buy one 🙄

I guess go for the largest capacity you can get and live with on a size basis.