Hi andrea
Look at post (earlier) from Sarah ( on removing tar).......
Euculyptus Oil is marvellous for removing tar, grease and oil (but as fellow abers have said caution to the material your dealing with!)......
I have used this method for some time - it is very good (clears your head too!), carpets, jackets, blouses (not silk) etc.
As bricro says vinegar is also good, as is Vanish (I have their soap stick [similiar to deodorant stick] it even takes out old stains - seems to work better than their liquid).
If you do read the other post I mentioned (the carpet I treated for a friend), the stain had been there for 6 months!