In a test environment, get hold of a nice box with lots of memory and use VMWare Server (its free). I create a seperate VMWare server for the APP server, JAS server, Deployment Server and fat client, and install the database onto the physical host. You'll need a TON of hard drive space though - I haven't been able to install a full E1 environment in less than 250Gb, and you really want some FAST drives otherwise the thing will crawl !
Beyond those boxes, however, you can then add additional Oracle boxes - including Fusion Middleware, etc etc
As for using Oracles Virtualization ? I wouldn't right now, last time I tried, it was REALLY tough to get configured and running. I'd stick with VMware at the moment.