I recently decided to dump my Oly 4/3 system and go Nikon- my first purchase is an old FA on Ebay, and also want to get probably a D300 in a while- what lens type should I be looking for? I know I can’t use Nikon "G" lenses on the FA- so what’s compatible with both? (I may also go for a D90 or D700) Can I use DX lenses on the FA?
Is this a good choice?

Nikkor AF 75-300mm f4.5-5.6- this is the older metal one, for $250 in good shape.

You cannot use DX or G CPU lenses on an FA – AI, AI-s, or AF in manual are the lenses you should get for the FA. For a telezoom, that lens is a good choice, but be aware that the FA is not an AF camera, so you will be focusing manually, and the lens will leave the viewfinder quite dim. The FA and FE lines were really designed for use with AI and AI-s lenses that are fast and bright. I would invest in a nikkor 50mm f/1.4 AI-s, I have one that I use with my FE2, it’s an excellent lens, and you can find them for around $250 on sites like KEH: http://www.keh.com/OnLineStore/ProductDetail.aspx?groupsku=NK060000250000&brandcategoryname=35MM&Mode=&item=40&ActivateTOC2=&ID=25&BC=NK&BCC=1&CC=6&CCC=2&BCL=&GBC=&GCC=

If you wish to use AI-s lenses on newer digital SLR’s, you should also be aware that unless you get a D300 or above, you will have limited use of them. They do not couple with the meters of lesser cameras like the D90/D60.