So I found this via a thread on Neogaf
http://www.neogaf.com/forum/showthread.php?t=865904Its basically a small program which will check your steam library for games which still have card drops left and then 'pretend' to steam that you are running that game to trigger the card drops.
When all the cards have dropped it moves on to the next game
You dont need to have the game installed , there are versions for Windows / Mac / Linux (and the games do not even need to be for that platform)
Its a random drop but most games with cards have around 4 or 5 drops , and most cards sell for somewhere between 3p and 10p in the marketplace (you will sometimes get a foil card which sells for around 5x the normal card cost).
I've been running it for a few days and its added about a fiver or so to my steam wallet , if you have a lot of games with card drops still available it may be worth a look
(I was originally running the Windows version via bootcamp but switched to the Mac one and it runs fine so while my machine is doing other stuff it can also be slowly grabbing steam cards to sell)