I'm trying to recoop some diskspace on a test SharePoint environment of mine. I've removed as much content as I can in the portal and also emptied the site collection recycle bin but the free space on the disk hasn't moved. What am I missing?
In order to recuperate the space you will need to manage your SQL Server database files (MDF/LDF). My suggestion is that unless your disk space is critical that you not do this. Shrinking databases has some serious implications for performance and can cause some headaches. IMO, unless you really need the disk space, just leave it.
Here are some sources to back this opinion up from SQL Server MVPs: