On our site we have always directed visitors to the homepage when they decide to continue shopping after adding a product to their cart. I have never seen any problems with it, until last week we received an email from a customer complaining that he wasn't taken back to the product page he was last on (the one he added to the cart).
Now our site is in an industry where people usually buy a couple of items...if that helps.
I plan on doing some A-B testing on this, but wanted to know what everyone's experience with this is. I have seen sites do it many different ways.
I send people back to the last page they were on, partly because of the way my site is set up. You can get on a particular product page and then just page forward or back from there to see each product in each group of products. I personally as a shopper prefer being sent back to the page I bought from. Sometimes sites send me back to the main page and then I have to go through a bunch of links to get back to the same section I was in.
vetofunk I have it both ways to the last page or to my catalog for more shopping this could be your front page. This lets them decide were they want to go. Sometimes a customer wants to make sure this is what they want and it is always good to let them make that decision.
If you take them back to the front page then they have to go about finding the product they just added and can be kind of a pain so best to do it multiple ways for the customers sake.