There are a couple of places on Bridges. The first one is towards the beginning, but you have to be careful as that area is a 2 way trail. When you go into Bridges on the right side of the parking lot, after the harder side loop, you run across the top of that little ridge, come out next to the board that seperates the trail. The section coming up where it goes back into the trees you need to carry alot of speed. When you hit the top of the little hump where it lets back out into the open, you can catch air off of it. Done right you don't get very high, but you won't touch down again until the bottom. But you have to be very careful of traffic from the other direction, as it is hard to see over the hump. The best thing is to send someone ahead to clear the trail.
The first of the big "dips" on Bridges, you can either hop off the top, or carry alot of speed and catch some air off the other side. I've also been jumping off the side of the 4th and 5th dip. Take a line about 12" to the right of the main line, just make sure you correct back towards the main trail at the bottom, and you need alot of speed to carry those moves off. Pulling up short could have bad results.
There are a couple of spots on Northcreek. The little hump that I'm sure everyone knows about, even by accident.
There is also a spot before that you can catch air going UPHILL. The trail makes a left turn and down a hill, you are going around a big tree as I remember. But it shoots you down this small hill, and then it goes back up onto a short ridge. Halfway back up thehill onto the ridge there are a couple of roots that have formed a small crest, simply loft the front tire a bit and you'll be suprised. Again, speed is the key here.
Disclaimer: I don't recommend this to anyone unless you have sufficient skill. None of these are easy, and all involve alot of speed to be carried. If done incorrectly you could get hurt.