I was searching how i can exchange my bitcoins online and i stumbled over this website that doubles bitcoins in 72 hours. initially i thought its a scam but i just decided to test with 0.02btc and later in the third day i checked my wallet and discovered i have been credited with 0.04btc.
Anyone interested can click: http://www.aftahost.com/
You can come back here and share you experience as i have doubled my btc 3 times there.

You should be careful with those sites. Don't invest more than you're willing to lose. And that's what's going to happen in the long term.

If you need let me know I can refer you one.