This is a website for renting a mining rig for short term gain. You get a set amount of bitcoins depending on the package you "purchase".
I've been using them for about 3 weeks now, and have gotten paid out multiple times. Most miners can make more mining on their own, with their own hardware, but this is a way to supplement your current mining income. I'm mining on my rig, and sending bitcoins to MiningUnited.com to make extra bitcoins. They seem to make their money off of Premium membership fees.
The current price structure for mining packages are:
0.05 for 3 days of mining will get you: 0.0662 back
0.10 for 3 days of mining will get you: 0.1339 back
0.25 for 4 days of mining will get you: 0.3517 back
I would suggest you check them out. (I do not own, run, or sponsor this website, just passing along information.)
http://www.miningunited.com/index.html
MOD EDIT:
Possibly a scam, read this thread
It was clearly a scam and I'd say your reputation is SHOT (regardless of your benefit from the site). You might as well resign from this board. I'm shocked that the moderators haven't banned you by now.