Oh, when I try to recommend friends her/TJ's stuff, it can be really difficult because I feel that there isn't any one song that defines her 'sound', especially up till now.
So if you don't want to go through her whole catalogue, I'd recommend the Watashi no Houden B-Side collection which has music from most angles of her career. Then depending on what sound you like, branch out from there.
Also, Tokyo Jihen's magnum opus IMHO is the Dynamite Out concert. The album it derived from is shittily recorded (She said that she wanted a garagey, 'unfinished song' feel to it) and while the songs are good, they sound like rubbish. Dynamite Out unleashes the full potential of most of the Kyouiku tracks.
She also released a solo album this year, which isn't as ambitious and is more 'pop' than her previous solo efforts (It even has rap), but it's still a solid album. My favourite track is this:
http://www.youtube.com/watch?v=JZRZe-nbhVY
It reminds me of psychotic, aggressive, evil J-Pop cheerleaders for some reason.