Mark,
The transponder frequencies are in the left most column on the Lyngsat listings for each satellite.
Alternatively, you can check out "TheList!", linked in the blue bar across the top of the Satellite Guys website. There are some active transponders listed in there.
Are you setting up a receiver? If it has blind scan, it might be easier to use TheList to aim the dish at a single TV station on a satellite and let the receiver discover the other transponders.
Martyn