Stumbleupon is a really inspired idea: you can review sites and tag them, so you add to the collection. There's a Stumble button you press and it brings up any website that's been reviewed by someone else in one of your preferred categories eg 'bizarre' or 'arts'. I posted some of my pages and friends pages and also played for a while and almost every site that I Stumbled on was worth visiting. It's certainly bringing a small but steady stream of people to visit my site too.
iloveyourtshirt.com - you can simply upload a photo of a t-shirt you want to promote and it goes straight onto the front page. Doesn't necessarily stay there long as someone else soon bumps you off. It's good though! I've noticed countries that don't normally show up appearing in my stats. Even when your picture has got bumped right down to the 10th page, it still gets click throughs : )