Good topic!
As for me, nostalgia is a big thing but I have to limit myself because they throw so much of it at us. My have very fond memories of my childhood and reliving that is great, I just can't wait to share it with my kids one day. The nostalgic stuff i'm collecting:
The Dark Crystal - my BIGGGEST weakness in nostalgia. This movie means a ton to me and I buy anything I can find related to it. Thank god for Plan B and now MINDstyle for keeping this property alive...
Star Wars - i'm 99% all OT with exception of Wookiees in PT...
Pee-wee's Playhouse - my favorite show as a kid. Hopefully NECA will release more reissues or new figures in general...
GI Joe - I tried to get into this line with other reincarnations but got bored, now with the 25th Ann, i'm rediculously hooked...
Transformers - I was always a HUGE Optimus fan since G1 so i've stuck to collecting anything that relates to him in the G1 era...
I do collect newer stuff and pretty much limit myself to specific lines but as the same with my childhood, it's all TV/Movie related and pretty much all cartoon based. The stuff i'm collecting now is Futurama, Family Guy, South Park, Milk & Cheese, Hellboy...