Definitely agree. Generally, I think good hacking music is unobtrusive (doesn't become a distraction), and somewhat repetitive (causes me to maintain focus). I hate a lot of electronic music because it's often too formulaic, but when it's right for hacking it's oh so right.
Some of my hacking favorites: Aphex Twin--Selected Ambient Works 85-92 (the one essential for hacking IMO), Sigur Ros--Takk..., The Field--From Here We Go Sublime, Linstrom--Where You Go I Go Too
Jeremy, fyi the player you're using:
http://listen.grooveshark.com/songWidget.swf
contains a flash stack overflow error in some effect event handling code that makes the page unviewable with the debug flash player installed.
Y'all should watch this video : http://www.vimeo.com/3734864 . It's an excellent documentary on the chiptune scene. Do a search on vimeo for part 2 and watch it before someone pulls it off.
There's also slayradio.org, which is mostly C64 remixes. It's mostly pretty fun stuff to listen to, although some of the songs get way too much playtime.
I used to listen to it but then I realized, "holy fuck why am I living in the past?"
Also, if you want sharp clean sounds you can listen to minimalist techno, some house music, etc. Most music is composed of sharp clean sounds because it's digitally recorded and fine-tuned by sold sound engineers.
Like with anything, creativity can spawn some really good 8-bit music that isn't only re-hashed zelda tunes. For a good starting point, have a look at that documentary I posted in the comments, I used to think it was just "living in the past" until I watched it and looked up some of the music.
Any kind of music with lyrics is to me very distracting while coding. Unfortunately the human brain can't really mix processing spoken language and written language.
Try writing while listening to someone, unless you're writing down what they say, you'll surely mix up somewhere and write down what they say anyway.
Edit: Less cryptically, this is all demoscene music -- the best minds of the last 25 years, remixed and mastered. Fresh every Monday, which gives me a reason to obsessively check my podcast list.
http://www.ptesquad.com/more/pte018.html