Oracle VM VirtualBox
If you haven't had a chance to work with it, consider visiting
It runs on windows, linux, mac os/x and solaris.
I downloaded a pre-installed VM with a database, development tools, and an application server pre-installed. Though I had the minimum required config (~2 GHz processor, 2 GB RAM), I was surprised that it ran as well as it did.
Though the initial setup is quite quick, the downloads of actual VMs to use in VirtualBox can take a while, but compared to the aggravation of pulling together Oracle 11gR2, SQL Developer, Apex, and a Weblogic server on your own, it's a more than fair trade.
If you've been putting off exploring Hands-On Database Technology on a home PC or a spare machine at work (http://www.oracle.com/technetwork/database/enterprise-edition/databaseappdev-vm-161299.html), then this could be a good way to jump in — with a virtual machine.