Account unlocks via web interface

I’m a network engineer of and Active Directory environment with over 150 employees, so obviously we get a lot of help desk tickets for unlocking accounts. I’ve been looking into setting up a web interface on our intranet so that users can unlock their own accounts, but so far I’m not thrilled with what I’ve come up with.

I’ve seen commercial products like EmpowerID, Self Service Admin, NetIQ’s Secure Password Admin, and
Avatier’s Password Management, but I’d prefer a free solution. I’d be willing to buy something inexpensive if it looks good, is easy to setup, and works.

Any suggestions?