I've raved about JazzStandards.com before. They did an extensive study of prominent recordings of jazz standards and ranked the top 1000. Discarding the obvious doubts of such a study (What makes a standard? Who's prominent?), their ranked list is useful for filling repertoire gaps or recalling forgotten tunes.
I made a list of tunes from those rankings that appear in The Real Book (Volume I, Sixth Edition). I included page number, rank, and title for each tune. I color-coded for ranking: red is top 100, blue is top 250, yellow is top 500, the rest are top 1000. To boot, I formatted it to fit on a single page, so I could paste it in the inside cover of my Real Book.
This is coming in handy. Part of my practice every day is learning new music. This gives me plenty of material, and it's roughly prioritized by popularity. And if everyone has this book at a jam session, I can glance over my color-coded quick list for a song to call instead of the entire index. I'll probably do the same thing for volumes II and III.