I got some tubes off eBay... every once in awhile you'll get lucky and can find some state-side for a good price (assuming your in the states) so you don't have to wait for them to come in from Europe. I got one of the PIC based kits for my Birthday this year... definitely hooked on Nixies now

The kit was IN-14s which are a pretty good size and were bigger than I expected. Since I wasn't expecting the kit, I had already ordered some IN-18s and they are definitely bigger. However if you are looking for a nice size at a reasonable price, the IN-14s aren't bad. Only part I don't like is they need to be soldered opposed to the IN-18s which are socketed.
-Mike