Here's something I found really useful. My ISP boots me after 45 minutes of idle time. However, it only checks for HTTP traffic. So, if I leave a download on ovenight and that download happens to be from an FTP site, I get booted after a while. So here's some source that I wrote to prevent that from happening. I just load the page in IE/Netscape (haven't tested it in Mozilla) and go to sleep. I hope someone else finds some use for it.
<title>Auto Refresh - Keep My ISP Connected</title>
<meta http-equiv="Refresh" content="900">
<frame name="main" src="http://cnet.com">
Edit: I forgot to say that what this page does is refresh the page in the <frame> tag every 900 seconds.