http://www.inspringitisthedawn.com/ and I indulge in a mini-readathon.
Basically it means read as much as you can/want over about 12 hours, and tweet about it periodically. There are other regulars, or semi-regulars who join in, and it's fun.
It's all about reading, catching up and sharing what you're reading.
We're having another one tomorrow, of a sort. If you feel like spending your Sunday (or Saturday, depending on where you are) reading, or if you have time for an hour or two, join in! :-)