Putting out feelers: Faster wheels for 26" mountain bike

My kid is taking over the lower-end '09 Cannondale F5 mountain bike that we got for cheap for me (...a size too small, just a bike for me to decide if I'd even want to invest more time and $$ into the sport, which I do).

Anyhow, the bike is DOG slow. It's a tank, but we suspect the wheels/hubs are the biggest issue holding it back. DS rode a friend's super zippy Salsa Ala Carte and now doesn't want to go back to the F5. Once I get my 29er we have to give her bike back, so we need to make the 5F a less sluggish bike for our skinny kid to fly on. We're going to change twist shifters, for sure, but it rolls so slow. When I've ridden it I thought I was dying, it's so slow. But it was the bike, not me.

Does anyone have any decent, maybe lighter, faster wheels that they'd be interested in selling? We're just putting out feelers on the off-chance that we can get a good deal on wheels that a kid is going to trash, most likely. :p