The Force.com Explorer (beta) is a new cross-platform Force.com database explorer built with Adobe Flash Builder for Force.com. It's an AIR app, so you can get started pretty quickly: click here to install.
Please send us feedback on improvements you'd like to see. Be gentle, it's still in beta! You can find a list of known issues below. If you discuss it in the discussion boards, please make sure to include "Force.com Explorer" in the title (or tag) so that we can find the posts.
This handy tool lets you browse your database schema, custom objects and fields, and build and test SOQL queries. It can also generate a simple schema report.