Military Aircraft Database, like an encyclopedia, few pics
Lorenz Bärmann´s german nightfighter page
Russian Aviation museum; excellent archive about russian aircrafts, like an encyclopedia
Luftwaffe ´46 - "what if?"
aviation site with many infos (in polish language, I regret)"
Nihon Kaigun; Imperial Japanese Navy Page
excellent source about the United States Navy in WW2
"The Hangar"
"Luftwaffe gallery, amazing photos!"
flying wings
"Uncommon Aircraft"
Totavia Aviation search engine
And here are some links for Trekkies:
my favourite Star Trek site
excellent photo collection of Star Trek ships
a Star Trek timeline
And here is a great meta search engine : Metacrawler