Here's a link to the source.
The current version is 1.03. GQuiz requires GTK+ 3.x to compile.
GQuiz's usable now. It's quite generic; all you need is a directory with a bunch of files, one file per (problem,answer) pair, and a program that will display the problem and answer. GQuiz just randomizes the order of the questions, eliminates consecutive repetitions (except for the last question), and keeps track of which ones you've gotten right "enough" times to eliminate (temporarily) from the collection, allowing you to focus on the ones you're finding more difficult and ones you haven't seen yet.
The rest of this web page is about go problems, the subject I originally wrote gquiz to drill on. There is nothing go-specific about gquiz however. To people not interested in go, this is merely an example of how to use gquiz.
I currently use gquiz with problems in five different groups:
If someone types in some free problem collection(s) (perhaps some of these), I'll happily put them up for ftp in conjunction with gquiz - but be sure to check with the problem authors before assuming the problems can be used for anything but private use.