Wow I wish I had thought of selling those on e-bay...
It's actually rubber garage door sealer that you can get at Home Depot for about $8. It's become somewhat popular in the WRX crowd now. Most people attach it with 3M double sided tape, but I've seen some screw it on also.
It actually doesn't look bad, but if you want to use it, please don't waste your money on ebay. Just go to the hardware store and save yourself $30. The shipping in that ad itself is more expensive than the product itself at the hardware store.
Edit:
Here is a "How to" thread on nasioc for a newer variation of the lip. Same basic concept though...
http://forums.nasioc.com/forums/show...hlight=diy+lip