About 60 or so I estimate. I've got 5 full sets of polyhedrals (the ones with the percentiles marked by 10s), 3 other sets of polyhedrals, and about a dozen or so more d6s (don't really know how many of those I got offhand). A pitifully small collection. I'm with Alzrius and Crothian on this one; not enough.
Every con or new game store I visit I "have" to buy a set of dice. I must have over 25 sets (7 to a set) plus several tubes of 6 siders and some of 10 siders plus metal and 2 inch sized and other goofy stuff. I figure around 300.
I went with the 41 to 50 range, but I may have a few more than that. I lost a large number of mine in lapse from gaming awhile back. Now I am making up for it by always picking up a new set to two at conventions.