Tossing my thoughts out, seriously cool site and I just listed 3 rigs on there.   A few observations, forgive me if they've already been made:

As a rig leaser:

List of all my rigs
Ability to mark all rigs online/offline
Allow renter to leave feedback so that people can know the good from the bad
Allow me to allocate more time to a person, ideally with a message sent to the renter.   In case something goes down I want to make good.
People that rent but don't send payment should have some sort of reliability rating, and then I can only rent to people with a reliability rating of X or higher.

As a rig renter:

Sorting of available rigs
Feedback method on person leasing rigs

Also, as a general thought, you've got no donate code on your site and I feel that after my first rental finishes I owe you a few coins

MightyP