The official Tiger (10.4) OS simply does not run in a virtualized environment. To get it to run you have to hack around the incompatibilities, which has been attempted with varying levels of (claim to) success, but it seems pretty sketchy. You're probably better off either dual-booting your MBP or finding an old used computer to dedicate to Tiger apps. I have a G5 still kicking around for just that purpose.
Leopard (10.5) and Snow Leopard (10.6) server are virtualizable and are fully supported by VMware Fusion. Leopard and Snow Leopard standard versions ("Client" version) do not support being virtualized. VMware Fusion 4.1 accidentally left out the code that prevents you from creating and running non-server Leopard and Snow Leopard VMs; version 4.1.1 was quickly released to restore the prevention code. I have not heard great tales of success or failure running the non-server VMs under Fusion 4.1, but you can give it a try.
All versions of Lion (10.7) support virtualization. The Lion retail license includes permission to create 2 VMs in addition to the one real machine so long as you run them on Apple hardware. Specifically, section 2B(iii) grants a license:
(iii) to install, use and run up to two (2) additional copies or instances of the Apple Software within virtual operating system environments on each Mac Computer you own or control that is already running the Apple Software.
Note that apparently Apple doesn't take this too seriously, as the official Lion licenses as posted at http://www.apple.com/legal/sla/ still require you to be running "Snow Leopard".