Alesis 3630 are the workhorse industry standard vibe. and give a good result on both vocals and drums. I use one on just about every session I do when I'm at work here
http://secretlevel.org.nz/index.php/recording-studio. Also the DBX 266xl or better yet the 166 are also really good little compressors and both the 3630 and 266 are pretty good price wise. the 166 will start to get up there at something like $300 US maybe? the others should be round the $150 mark (these are all retail not second hand though) heaps less second hand. depending on how crazy you want to go the "distressor" is probably a better way to go. they are mono so you would need two to do a stereo job and are quite expensive but you will never need another hardware compressor for drums or vocals ever again. (i'm saving up for a couple at the moment).
thats my two cents anyway.
peace