Thought I'd share/make note of a few (Windows [Vista]) tools I use for my image files.
Bulk Rename Utility
Exactly what it says on the box: It lets you rename files in bulk. It doesn't look particularly pretty, and the load of form fields/options at the bottom may be intimidating at first glance, but I found them pretty self-explanatory when reading them one by one.
I use the "File" field on "fixed" setting together with Numbering to change the filenames of photos I take from IMGXXXXXXXXX.jpg to 2009-07-21_XXX.jpg, which helps a lot with sorting them.
iTag
With this program I can add titles, descriptions and keywords to jpg files. This is not only useful because the Windows Explorer can search these fields, but also because various websites and scripts pull that information out when you upload them, including Flickr, Picasa, and Menalto Gallery2. Saves some work if you upload your images to several places.
iTag is my favourite among the tools I tried so far because it lets you include linebreaks in the description (unlike Picasa or the function built into Windows Explorer), and ladjust the size of the form where you enter things - particularly the fact that the latter enables you to view all keywords you entered on an image.
SyncToy
...is not only useful for images, but all kinds of documents, but here goes: A very basic program to synch up different folders. I'm sure there are better ones, but this works for me.