I have been having to enter my password everytime I access the svn server with tortoisesvn and it was finally getting annoying enough that I did something about it. I already knew how to set up a public/private key pair for the command line svn client. To do the same for tortoisesvn you follow the steps detailed here<-(link broken see below), in the section: SSH key generation and connection check (client).
Update: Here's a new good link.