I recently joined a photography challenge being organized by Vicki of Knitorious. Basically, she's broken the year down into two week segments and assigned a letter of the alphabet to each. The assignment is to take a photo (or more) of something that represents each letter to you.
I've never taken part in anything like this before, but it seemed like it would be a fun thing to do, something to keep me thinking and maybe zip up my photography a bit (although I've just been looking through my recent photos for the first few posts, now that I'm involved, I anticipate looking through the camera with a "new eye".)
It should be fun to peek around at what others are posting too.
I posted a link (a bit of a challenge for me to sort out the html tags to make it work) on my sidebar, so, take a look at what others are doing.