I started "practicing" my interview skills a few years ago by... interviewing with companies. Interviewing is great for keeping your skills fresh, for learning new things, and for meeting cool people working on cool projects. It's a lot of fun! And it has the added benefit of giving you opportunities at new companies, if you end up finding a better position than the one you're in. Just keep it on the DL from management at your current company. For some reason, they don't like it when employees do that.