Depend on the part? Local if you can? good sites other than for sale here for afer market parts/accesories? Not sure what I Am looking for yet. Reciever hitch maybe? Subaru quite a bit diffrent than the jeep world I was used to. Not sure what direction the subaru will go yet. Nothing too wild Im sure.
eBay. I bought alot of my parts on eBay. OEM parts: Morries Minnetonka. Also, the vendors on here are decent. Now, a flood of retards that don't know how to research or pay attention will relay their story about how they got screwed over on eBay or how all eBay stuff is crap, even though you can buy brand name **** with no sales tax at wholesale prices if you are smart.
Anywhere but ebay. lol, no seriously, for aftermarket parts ebay, wholesale retailers, groupbuys (through various forums), pre-release groupbuys, or call up vendors asking for price matching and combo deals. For maintenance and replacement parts either the dealership or rockauto (depending on the part).
Import Image Racing. Best prices hands down They actually support MNSubaru with PAID advertising. GrimmSpeed for any GS parts
I buy used parts off here or nasioc... be careful who you buy from on nasioc however, I've been burned numerous times.
I usually buy all my parts from various forums...mnsubaru, nasioc, clubwrx, rs25, iwsti, I will purposely search all the forums before i buy new. Maybe becuase im a tight wad, maybe because its smart?
I steal and rob for my parts. Keeps my overall costs low and adds a bit of excitement to it. Like the others have said, for OEM stuff I go to Minnetonka. They take great care of us club guys and they've got a ton of knowledge to share. For aftermarket, I try to support decent vendors. Kartboy, IIR, Turninconcepts.com, RaceComp Engineering and Grimmspeed come to mind. There are deals to be had on Ebay, but only go through well known and good feedback rated sellers.