For Onsite clients....

[Cadishead Computers]

+1 on Martyn's bag. One of the best bits of kit I have ever bought. What you can't fit inside the pockets is not worth talking about. From memory, it was around the £40 mark last year.

(Had to buy another, as my last one was stolen in Apr 11, in the 2nd break in). Not to mention all the assorted tools too. Made for a expensive bag..

[HCHTech]

I use this. It's a little garish, but works really well.

There is another thread earlier this year - you should search it out for other options.

I also carry a laptop bag with files, a cellular netbook, and a very few other items. I leave the heavy tool bag in the car until I need it.

This has been a huge improvement, back-pain-wise.