I love discovering fun online tools, especially when they're free :)
Dumpr is a photo and image editing tool that I came across at the beginning of the year. It has some really nice effects available. A few of the effects that used to be free are now part of their paid "pro" package, but there are still enough free ones to make it worthwhile checking out.
I especially like the Amazing Circles effect. It doesn't work well with every image, you'll have to try a few to find out for yourself which ones you like. Here are a couple that I think turned out well - I've included the originals here for comparison.
Tulip at Floriade 2007 with Amazing Circles effect applied:
Original photo:
Lotus pond at Botanic Gardens of Adelaide with Amazing Circles effect applied:
Original photo:
I also really like the Rubik's Cube effect. The Christmas Ornament and Museumr effects are cute too :) Why don't you give it a go?