As I mentioned previously, I've become quite taken with podcasts recently. A Podcatching application is a type of aggregator which periodically checks for and downloads new content automatically. When I first started listening to podcasts, I'd download Ron Moore's Battlestar Galactica podcasts as mp3 files and listen to them with winamp. It wasn't until I found a few more podcasts I liked that I looked into podcatchers.
Each of the podcatching applications I'm going to review here has a number of different features, and I'm sure that different podcatchers will work best for different people. I'll do my best to remain objective and say why I liked one over another.
The first application I tried was Primetime Podcast Receiver, which was really a very good application. It's lightweight, does a good job of organizing the various podcast feeds and displaying show notes, and sits in the system tray where you can play, pause, and stop your podcast from a right-click context menu. However, it doesn't let you decide what directory you want your podcasts saved in - it just throws them in its own directory - assumedly in Program Files. Also, it only allows you to play the podcasts from its integrated player, unless you feel like hunting down the mp3 files in the Program Files folder. Still, all in all, this is one of my favorites.
iPodder is a good solid open-source application of which I've become quite a fan recently. It lets you save your podcasts in any directory you want, and has a beautiful tabbed user interface. Viewing the show notes is a pain, since you have to choose a right-click option which launches your browser, and the program is set up to only use iTunes or Windows Media Player, but its' interface more than makes up for it. You can select a podcast and view all the shows in its XML feed, then select only certain episodes for download. This, more than anything, is the reason I use iPodder over the other applications. You're not limited by date ranges - you can pick and choose any episodes you like. Very nice.
iPodderX is the fancy boy of the bunch. It's got a lot of features, and a very pretty UI. Like iPodder, you can only play podcasts in iTunes or Windows Media Player, and like iPodder, you can pick the directory in which to store your podcasts. But iPodderX downloads all podcasts in a given feed without giving you the option to pick and choose which, or even to view the individual episodes until after they've been downloaded. That for me was the biggest minus. It's also got an integrated browser to display show notes and a diskspace-based cleanup tool that will delete old podcasts based on how much space they take up.
Doppler Radio is a simple little app that lets you play your podcasts from any player you like. (yay! I can use WinAmp!) However, its interface falls short. It's all right-click context menus and popup windows, which I find annoying.
Odeo is very different from any of the other podcatchers in that it is web-based. Personally, I'd rather use a client-based aggregator, but I know plenty of folks who love Odeo. From what I gather, you can either download and install their Odeo synch program or simply use a custom-built XML feed which feeds you the podcasts you've selected on their website.
There are a number of other podcatchers I haven't tried, such as jPodder and Blogmatrix Jager, but the ones I've reviewed should give you a good grasp on what's out there.