I need help.
My current puzzle collection consists of a few regular Cubes, a Pocket cube, a Master cube, a Bandaged cube, a Siamese cube, a Skewb and a Square 1. My question to you all is:
What would be a good next purchase?

...go for another Archimedean solid. Tired of cubes? Try a sphere, or a tetrahedron. There's plenty of each to choose from: Rubik's World, Meffert's puzzle balls, Pyraminx, Pyramorphix, the Hungarian Globe, Mozaika, Masterball, etc.

Hope this helps!
Jason

Don't forget the Dodecahedron! You have two to choose from: Skewb Ultimate or Megaminx. Both are available at Meffert's site.

I'd pick the Megaminx (a.k.a. "Magic Dodecahedron") because it has different guts/internal mechanism than the others. The Skewb Ultimate (a.k.a "Pyraminx Ball") is really just another Skewb but with different exterior geometry.

On ebay you can find an alexander's star. It's a great puzzle and usually sells for $15 at most. Some of the others suggested go for much more. Also try rubik's clock or one of rubik's magic puzzles. Enjoy!
Michael