Central Ohio Paintball
My closest proshop.  Gotta support the locals.
Links
Countypaintball
The biggest selection of Pro/carbine parts and accesories.  They carry the Stabalizer too.
WARPIG
A great place to find just about anything paintball related.  Reports on new products(usually not for the P/C)

Have any suggestions?  E-mail them to me @ buckeyevs@yahoo.com
Stores
Info
Manufacturers
SOG
The site of a team.

Tippmann

AirTipps
The maker of most of the Pro/carbine accessories, for now.  Their products are sold exclusively through Countypaintball.com
As far as I know, the manufacturing side of Air-Tipps is no more. 
Palmer-Pursuit
The maker of the Stabalizer regulator.  I have one on my gun and it is very consistent and I almost never have to adjust the velocity. It always chronoes in where it was last time I used it.
PaintballGear
Just because I know there there.  You can get some other non-p/c specific things there for a good price usually.
Matt's Pro/carbine Page
He has every do it yourself modification that you could think of listed  Some that even seem pointless "I'm bored" mods.
A-1 Paintball
They have a lot of content that might be interesting.


A-1 Paintball
They have a lot of content that might be interesting but nothing specifically for the P/c except stock parts..


JCS
A source for folding stocks, sight rails and a bi-pod.
The Paintball Store.com
Some barrels.
Me
With the leaving of Air-Tipps, I have started making RVA's to help fill this need.
I have also begun performing custom modifications to use Tippmann's Flatline barrels, feed systems, and firing systems on the pro/carbine.  To complement the work I have anodizing capabilities as well.

Tippmann Parts
This is a great place to get replacement stock parts and a couple of other accessories.