First off, if you're going for Tygon R-3603 tubing, make sure you get sizes with a 1/16" wall. 1/8" wall will not fit ANY current compression fitting.

Second, may I suggest R-3400 tubing? It's basically the black version of R-3603. I know it's a modders no-no to use anything other than clear tubing, but if you're a newcomer to water cooling, clear tubing is a pain. Clear tubing excites algae growth and until you figure out the correct mix of corrosion inhibitors and algaecides needed in your loop, you may have problems. Just a suggestion though...

Third, G 1/8 or 1/4 compression fittings from AC will fit Tygon 1/4" ID x 3/8" OD x 1/6" WALL diameters, of any composition. These fittings are available from sharkacomputers.com or *other* vendors with Innovatek products.