Here's a pretty cool site that creates a .res file and allows you to add your most frequently played servers directly to the game menu.
http://www.specialattack.net/tf2/game-menu-generator
Just add an IP to the "add custom server" box on the right. Then drag them from the "custom servers" box at the bottom up to the "selected servers" box up top. Click the Generate GameMenu.res button. Save the file and then add it to your "team fortress 2/tf/resource/" folder.