Decent prices and a pretty good selection of sizes, shapes and cutter styles. I picked up some high-helix cutters to try out the last time I bought stuff. They kind of split the difference between the full aluma-cut and single/double-cut style that's more suited to iron & steel.

You can use single/double-cut on aluminum, but absolutely must use grinder's grease (like a wax stick) or some type of fluid that helps resist the clogging issue. Also, keep a stiff wire brush handy to reduce the buildup before re-treating the cutter regularly during use.

I used to get my carbides from the Mondello Technical School before ol' Joe passed away. I don't know what they even sell any more, if anything, since then.