The 12'x12' monster tarp from Guide Gear is $20 again (white only). It's big enough to get two hammocks side-by-side under a single tarp for the honeymoon suite or makes a great Baker Hut for a tall guy.
IF you find the right two trees (BIG ONES!), it's over 16.5' on the diagonal so you can hang two hammocks feet-to-feet both from the same two trees. Overlap the feet slightly and point the heads both towards the trees. As long as you both sleep on the diagonal, it works great and you end up with ridiculous amounts of covered area on each side.
Note that none of the edge tie-outs are in the middle of a side. They're on the corners and then every 4' around the edges so if you want to hang it as a straight A shape, you need to add a pair of tie-outs or get the tarp tie doohickeys from JRB. I remember being surprised by that when I got mine (for $25 ).
Dirt cheap and much lighter than something from Home Depot.