If you want new -
LH ( passenger ) door part number 60617925, RH ( driver's ) door p/n 60617926.
About £38 each as at Feb 2010.
The outer ones aren't too bad to remove/replace with the window in situ ( the ones inside the car are much more difficult ).
remove the plastic rivet at the end
remove the 'U' shaped plastic locking bar ( it runs the full length of the seal )
ease the old seal off the clips ( careful you don't break the clips )
fit the new seal over the clips
replace the U shaped locking bar
replace the plastic rivet.
Parts diagram here
Item 3 are the clips - there are quite a few of them
Item 6 is the U shaped locking bar
Item 'A' ( top left ) is the actual seal.
I think the £38 actually buys you both the interior and exterior seal as they are both labelled 'A' and there's only one applicable part number.
Probably a lot easier to get a good used part!
It's awkward to do with the glass in place. It's just about possible for the outer seal but the inner seal I found impossible without removing the window as the gap between the window and door metal is so small.