Well, if you havn't heard of Tiger Mountain, t hats definetly a spot you should check out for some nice downhill. It is closed now, but should open up around April 15. But the trail closure on Tiger doesnt afect the whole mountain which is looped with logging roads. Some of the views up there are great and are well worth the climb.
As far as nice single track, I would hit Tolt Macdonal, which is in the city of Carnation. Although this is a ways away from the Kent area, it would definetly be worth a shot for a short day trip. What you want to do to get to this trail is to drive into carnation (yahoo map) and look for Told Macdonald Park. Follow hte road back into the park and there should be a parking lot. From there ride you bike over the bridge and up the dirt path till you come to a little cabin. Behind the cabin is the entrance to the trail system. I would highly recomend a rider who knows the area here because its very easy to get lost.
Cose to Kent you have Philop Arnold Park(tapeworm) which has some nice twist single track but also some real nice, real big dirt jumps. Aroudn the dirt jumps are plenty of smaller drops. Lots of fun stuff there.
If your living in the south end, I would also recomend you try our Victor Falls and Lake Sawyer. I have never been to those areas, but have heard many good things about them.
If you have no idea how to get to any of these places do a yahoo map or go to any lbs and they should know where your talking about.
So Tiger for downhill.
Tolt for single track
Philip Arnold for single track and jumps/drops
And victor falls and lake sawyer for single track and......stuff.....