I really like my Wilderness Logics Tadpole (about $85, but can be found cheaper if you watch the for sale section). Here's a link to a video I did about my set up, you can get a pretty good idea about the tarp from that.
I also really love my Warbonnet Superfly. Cost a bit more and weighs a bit more, but you get more coverage and the built in doors are great (about $130, but again, can be found cheaper if you watch for them.....although, these don't go on sale too often)
Here's a pic of mine in action during the snow we got for Christmas.
If you want a bit cheaper, check out the Chinook or Kelty tarps. I've read a lot of great things about them, but you will feel the savings in the extra weight. They are pretty heavy.