I've personally used the Mushkin Blue line, a pair of 256mb modules. They were very stable, and allowed me to overclock without causing havoc.
If you buy
directly from Mushkin, you get some outstanding customer service. I had to replace a module once, and they had a replacement shipped overnight so I wouldn't have much downtime (a standard procedure as far as I know.)
Mushkin is pretty cool, and their memory is cool (and functional) too. I have never used Kingston anything, so I cannot vouch for the performance.
- rp