Can anyone recommend the some services that monitor individual websites? Your help is greatly appreciated.

what do you want to monitor?

what do you want to monitor?

I would like to be able to be notified if the domain is unreachable for any reason.

hyperspin.com, host-tracker.com I expect there are completely free ones too, but I have yet to find any, although it would be nice.

I would highly recommend Hyperspin or Pingdom.

Although, if I had to pick one... I would pick Hyperspin for the extra features, such as the ability to disable monitoring for scheduled maintenance, etc.