A mixture of several topic-specific Moleskines, some A4 pads, post-its, blog, diary and word processing or calendar software. If it's a thought that's linked to something else, or a date, I often (in true GTD style) associate it with that date or object. Most of the time it's my "work", "home" or "daily" moleskine that gets the brunt though. And although they're not searchable, it's so much fun flipping back through them...