By popular demand ("this one guy asked for it once"), I've added a post index to iRi. (Also, Google has lost a lot of my pages, which sucks mostly because I keep trying to use it on my own site.)
I tried to implement something like Amazon's Statistically Improbable Phrases, which take characteristic phrases out of books and works pretty well, but my corpus is too small. There are many words I use only once, and the vast majority of two-word phrases are entirely unique. Consequently, I use only single words, and even that works poorly.