Put a miniature, actively-updated version of a window on top of other windows
http://www.klopfenstein.net/lorenz.aspx/ontopreplica
I've seen this before, but this program has really come a long way since then.
I've recently started following an irc channel (#spree on FreeNode), and I like to see the relatively infrequent updates, but it's a pain to keep remembering to switch to the window. By the time I do, there's no chance to participate.
I vaguely remembered a program that would let me make a miniaturized version of a window that would stay on top of the others and actively keep pace with the content of the original window. I couldn't remember the name though, and had a hard time getting google to understand what I wanted (a frequent complaint when trying to search for window-related software in Windows, imagine that).
Finally I found a cousin to the program I was thinking of (don't remember the original, but it was different). I'd also seen this cousin at that time, but wasn't impressed enough with either of them to keep one.
This time around, though, it looks like this is a fairly mature implementation, with lots of useful options (opacity, sizing, storable settings, region selection, click-forwarding, etc). It's now showing me just the bottom of the irc window where new comments show up. It's at 50% opacity and 1:1 size so the text is completely legible. Even better than miniaturized.
A quick search at alternativeto.net showed that the only other well-known option is a Mac program, so I don't know what happened to the other cousin, but I'm not worried.
You can't get the installer from codeplex (just the executable), so get it from the main site linked here.