If you've ever had a hard drive die on you, or had your computer stolen, you've probably come to appreciate--and possibly have shaken your fist at--computer backup. Bad things happen, which is what makes utilities like FlickrDown so darn useful.
This small Windows application provides a simple way to pull down a large portion of your Flickr photos at a time. You just give it your Flickr credentials, pick which sets of photos you want to download and it does the rest--putting them in tightly organized file folders on your local machine. Sure you could just download the original of each shot from Flickr's pages, but that doesn't scale.
The app requires at least version 2.0 of Microsoft's .NET runtime, which you might already have installed if you're a user of Paint.NET. Also worth noting is that the tool cannot pull down any videos you've uploaded. If you want to do that you should check out a tool called Orbit++. There's a good tutorial on how to do that here.
In a time when Yahoo is heavily promoting its "open strategy," Flickr is not quite there yet. The service still does not offer FTP access for its members (free or paid) to be able to pull down full quality versions of their shots en masse, however the application programming interface has allowed for several workarounds like this that--unfortunately--require extra software.