In the way of new materials, you have the plastic ones (Fobus) and the thermoplastic ones (the various Kydex holsters). I don't have any experience with plastic, but the kydex models offer very solid retention but smooth draws and returns.
For the cheap ones, I have an Uncle Mike's and get good mileage out of it. Very solid basic Kydex, for ~$20. Add $12 for paddle (I use the basic belt model, works fine, just need to thread it).
Other companies to check out are Comp-Tac and Blade-Tech. The latter makes very nice mag carriers as well.
Expect about $60-80 for a Kydex holster from a 'respectable' brand.
All very economical compared to most actual leather ($70+++) and money well spent.
Glocks seem to have the highest attach rate when it comes to aftermarket gunleather, after 1911s. Chances are, if they make a holster, they make a Glock holster.