Good tool to monitor your site/server?
 

Can anyone recommend a service that monitors your sites and notifies you when its slow or down?

there was a thread with new service recently.But personaly i think best would be to install script which can do that things for you and notify you in case high load or offline apache.

I've been looking for a while something that will work with mrtg and will notify by email or sms if bandwidth goes above a certain point. Would love to have that.

You would need both incoming and outgoing ... You should see hom many box have port scan installed without the knowledge of the box owner ... taking from 2 to 4 mbps....

This does it all and Way more.
http://www.woodstone.nu/salive/

On our todo list is a tray icon which will graphically show your mrtg traffic, load
average, etc. It'll be green for "normal", orange for high, red for oh shit, etc.
That'll let you keep on eye on the overall status very easily out of the corner of
your eye. We'll integrate it with our existing simple server monitoring which
we do for some people. That does send email and SMS. This isn't something we
generally market - just something we use to monitor our servers and
for a few people who asked about it.