Can someone reccomend a good and easy to use Database Manager for Mac?

I recently had a web firm create a website for me. I’m trying to learn how to manage my users. I am used to doing this with Joomla/JomSocial but since this is a different kind of site, Joomla was no used. I need something I can use for my mac that will allow me to manage users.

Any suggestions? The best free one.