I wrote a tiny application which makes it easier to copy the text from a file to the clipboard. It's a shell extension which adds a new entry to the context menu in Explorer.
To install it, just run it once. In Vista, you'll have to use 'Run as Administrator'. Now you'll have a new menu item in Explorer's context menu, which looks like this:
This program requires the .NET framework version 2.0.
Here's the binary: CopyFileContentToClipboard-1.0.0.1305.zip
And the source: CopyFileContentToClipboard-Source-1.0.0.1305.zip
Released under the MIT licence. Based on a sample application written by Ralph Arvesen.