What are your requirements? IE passing through a firewall or pesonal router?
I still like the MS client and I just port forward the RDP port, crap I forget the port #. Aahh it's 3389.
In the past I would run Dynamic DNS Free
on the XP box and forward the port requests from my wireless N router to that box. I ran TightVNC but switched to UltraVNC for the added security. I'd log into the XP machine periodically from my office to do a number of things (start a download, check out how a site rendered from home rather than the office, etc.).
Also www.logmein.com is a web based remote application and you get 5 clients for free
Is this fairly secure?