Another up and comer, currently in beta but very stable on my machine after 3 weeks of testing is Jetico. I currently have the 1.0.1.31beta which is the current beta version and so far haven't found a single thing to report. It's light on resources, stealth everywhere, somewhat confusing but not difficult to set up, and it just works. I'm running Win XP Home SP1, 1.3G Athlon, and 512 RAM. Anyone interested in testing it, it's available at the addy below. The beta is free and is upgraded as needed.

http://www.jetico.com/