Being a professional programmer, text is very important to me.  My professional work-products are all text based files (with extensions of .cs, .java, .aspx, etc)  Having a good set of tools to work with text in your toolbox is important.

One of the tools that I use constantly is BeyondCompare.  The program is just excellent, it takes any two files and puts them in two panes of a window, side by side, highlighting the differences.  Using your mouse, you highlight each differences, and then "copy left", or "copy right" in order to synch up the files.  It even works with files available via FTP, allowing you to compare a local version to a version on your server, very handy.  To top it off, it runs off a USB key, so you'll be able to compare files wherever you go!

I just found out today, I can use BeyondCompare as a replacement for my Tortoise SVN "diff" program.  Go to "settings", and change the "external diff viewer", slightly obvious, but I didn't know about it until today!