8 speed shifters work with 9 speed deraileur/casette?
 

I'd like to upgrade my casette / deraileur to 9-speed for now because my casette is worn and i have to replace it, so might as well make the jump from 8 to 9 speed.

however, i don't have enough cash to drop on new shifters, so can i just use my old deore 8-speed shifters with my new 9-speed setup?

Cogs on a 9 speed are closer together than an 8 speed, which is why 9 speed must use a narrower chain. If you are changing to a 9 speed cassette, go with a 9 speed shifter-and you'll need a new chain for 9 speed also, but should replace the chain anyway if the cassette is worn enough to need replacing.

What you'll need to go with the new 9sp cassette is new 9sp shifters (and 9sp chain), the "8 speed" derailleur will do fine (the "speeds" are in the cassette and shifters, not the derailleur)-

Ah, i see. Actually, that makes sense now that I think about it. Thanks!

Oh and what about my chainrings? Will those need to be swapped out as well?

Your chainrings should be fine-

No need for a new derailleur, and 8 speed cassettes (at least road ones) are cheap. What range are you looking for?