What do you guys do to cure winter riding blues?

For all those posters who are blessed/cursed with significant snow all winter (and don't have a cozy indoor arena) what do you do with your horses? Often times the footing isn't good enough to do a full workout, so I'm looking for any interesting suggestions!

When I can ride in the winter I do a lot of walking. Direction changes, halts, speed variations within the gait, turns, etc. It isn't much, but it satisfies the itch a little and does something useful for my horse/training. I try to continue exposing them to new things too, but it gets difficult with really deep drifts and/or ice.

By the time spring rolls around we've got things going really well at the walk so it's easy to translate it to faster gaits.