I have an 8gb Ultra Sandisk that gives me 250 raw and jpg. I also have a 4gb and 2 x 1gb Extreme III and a 4gb Rdata card.
I buy what's affordable, currently I have 2x16gb Kingston elite pro cards which have been rock solid in the 5d, plus an 8gb sandisk ultra ii which is seldom used. I've just added a 7d to the bag so another 16 or even 32gb card is in order, pending some testing I'll probably go for the Kingston cards again.
I use 2 Sandisk Extreme III & 1 Sandisk Extreme Ducati SDHC cards, all 4gb each. Mainly went for Sandisk for reliability reasons and went with 4gb mainly so if a card did become corrupt I wouldn't loose everything. I have been thinking about getting a couple of 8gb cards though, mainly because I do some motorcross photography and would rather not have to change cards as much. The class 10, 30mbs cards may even help to get more images with their faster read/write speeds. I only shoot in RAW mode so the extra room will get me more than the 166 Raw files that fit on the 4gb cards. Will probably get Sandisk again but may look at other top brands like Lexar etc.
Pentax K20D & Grip, Sigma 17-70 f2.8-4.5 DC Macro, Sigma APO 70-200 f2.8 EX DG HSM II, Metz Mecablitz 48 AF-1 flash, LowePro Flipside 300 backpack, Photoshop CS 5, Lightroom 3, Manfrotto Monopod & 498 RC2 Ball Head, GoldPhoto "Tracker" Tripod, Hoya CPL and UV filters, Yongnuo RF602 flash triggers.
The 5D gets the 4g cards, I have 2 of these
The 7D gets the 8g Cards, I have 2 of these
This gets me in the area of 300 RAW on a card with a back up card if I need more
I also have 2 x 1g and a 2 gig card just in case I need a little more space in an emergency
I never take my cards out of my bodies, I always download via cable. I run an 8gig in the 450D & a 16gig in the 50D. I thought about buying a 32gig for the 50D but have not been game. Don't ask me why because I don't know. When we go to the States next year I will probably buy another card as a backup for the 50D, but have not decided on whether I'll buy another 16gig or a 32.
Lloyd
Canon 5D2+40D+L+Σ+S100
Never make the same mistake twice, there are so many new ones, try a different one each day
Flickr
A couple of Sandisc 4GB's, one for each camera, that's all I need.
John.
Canon EOS 50D
Panasonic Lumix TZ10
I run with sets of 16GB cards, since I tend to shoot in RAW all the time (and sometimes with JPEG for previews) on a rotational basis. Will probably pick up some 8GBs as backups. Known brands only (as usual).
Adam