Depends
If you just want to try out various operating systems, set up test environments and the like, VMWare Player or VirtualBox running on windows are fine. Both have been rock stable too so the only real pain is the overhead of the background OS. They also give you familiar easy ways to access the filesystems behind the scenes, make backups and so on. i.e. for most home use, fine.
Want to step it up a bit - basix ESXi or HyperV are both free (I think...) but both more difficult to use and (esp. ESXi) create some hardware restrictions, quirks like access to VMFS etc. Only really for businesses or people who want to geek-out a bit.
Biting the hand that feeds IT
