One of the important thing for a VPS is uptime , just share with you some of the FREE monitoring service out there.
- Siteuptime – a very traditional site uptime monitoring service, max interval is 30 min.
- Montastic – selling point is having RSS feed for status, i use this in my netvibes, so that i can monitor my site most of the time ( since i on my netvibes most of the time), It also provide yahoo widget for status checking
- Site24X7 – a monitoring service by Zoho , it include alert by email , SMS ( SMS alert too for certain area) and RSS , i believe the best part would be the report part, it include daily/weekly report about your site uptime statistic.
Also try http://mon.itor.us – free monitoring with Ajax interface, also provide RSS feeds, real time performance charts, customized desktop view and many other interesting features