Are there any good and recommended website speed monitoring softwares to record speed and downtime continuously? Any free alternatives?

TIA
Jeff

Pingdom will record the average latency (daily) along with any downtime.

Link:
http://www.pingdom.com

siteuptime and host-tracker are good for downtime notifications... sometimes they're a few minutes late, but they're pretty accurate.

Check siteuptime and alertra.com

I have started using SiteUptime.

Is there a software like siteuptime that can detect lagtimes as well and not just downtimes? By lag times, I mean slow times.