Q. How do I make a RAM disk in Mac OS X?

A. RamBunctious 2.0 (review)

A. Alternate viewpoint: Why you don't need a RAM disk on OS X

Q. How do I disable virtual memory?

A. From the CommandLine:

[localhost:~] you$ sudo pico /etc/rc 

Scroll to the very bottom and comment out the line that starts with "dynamic_pager". Changes take effect on reboot.

Q. Can I put my VirtualMemory swap file on a separate partition? Should I?

A. Yes, you can. Here's how: How to: Move your OS X swapfiles to a separate disk to improve virtual memory performance

Or here: Using a Dedicated Swapfile Partition to Speed Up MacOS X

Should you? That depends. It does help. Putting it on a separate partition can avoid fragmentation of the swap files. I have been told that putting it on a separate hard drive on a separate bus (where you can physically read the two drives simultaneously) can increase performance dramatically. Your mileage may vary.

NewInJaguar: Mac OS X Hints: Moving swap in 10.2 revisited