What is your strategy for limiting computer time?

I am trying to begin using some tips and suggestions that I have found in various ADHD books to treat some of my symptoms.  One of my biggest issues is extreme HYPERFOCUS.  I can get really obsessed about something and cannot seem to balance it with other areas of my life.  One of the ways that I really struggle with this is trying to make myself get OFF the computer after a reasonable length of time.  I can surf for HOURS and it feels like minutes!  This frequently interferes with other things I need to do (like going to bed at night!  It is 12:10am right now.).  Can anyone share a strategy that works for you on helping to limit yourself on the computer?  I can get on Facebook or a site like this and read blogs and posts for hours and if I am researching something, I feel like I have to see ALL the resources available.  Links are never-ending...You can just go here and there and everywhere on the Internet!   And I can't seem to stop myself.  Sometimes I forget to eat!  Help!