I have used a lot of different brands of coconut milk and my personal favorite is Whole Food's 365 brand, especially when using light coconut milk. It is also organic and not too expensive.

I 4th the Chaokoh brand. In a pinch I'd use Thai Kitchen.

I agree with the above posters. Also, watch out if you are shopping in a big American grocery store. I've seen sweetened coconut cream in the 'ethnic foods' section instead of the alcoholic mixers section where I think it belongs.

REALLY be careful--just look how I mis-spelled Chao Koh!!

Kasma Loha-unchit, a well known Thai cooking teacher recommends Cha Koh and May Ploy. Be careful though, there are brands with similar names.
http://www.thaifoodandtravel.com/ingredients/cocmilk.html

Chaokoh is a good brand; you'll find it in most Asian markets and often in the mainstream markets. A Taste of Thai is good, and I like the (cheapest!) one that Trader Joe's sells. But for the best flavor and richness, I usually go with Chaokoh.

Here's a link to what the can looks like:
http://thepurplepepper.files.wordpress.com/2010/05/coconut_milk.jpg