WUU claims to be "a program to keep your mods updated with the most popular mod sites. It supports WoWAce, WoWInterface, UI.WorldofWar.net, Curse-Gaming, AuctioneerAddon, GathererAddon, CosmosUI, CTMod, CapnBry, GoogleCode and AceSVN."
I downloaded the zip file, extracted it to my desktop, so there's a handy WUU folder, and then went inside and blindly ran WUU. I was greeted by a blank screen. I didn't know what to do at first, so for your benefit, I'll direct you to the AddOns menu. It contains everything you'll run on a regular basis. With that knowledge, you can dive right in with these quick instructions:
Run the software, tell it your WoW folder, *NOT* your AddOns folder
Press "ctrl-D" to scan for your addons
Press "ctrl-M" to figure out sources for AddOns from the Master List (WUU comes with a list of MANY mods and where to find them)
Press "ctrl-D" again, so that you see ? next to the local versions
Press "ctrl-V" to check what the online versions are
Press "ctrl-U" to update your AddOns to the newest versions found online
That's it. Now, it won't work flawlessly. At the end of it, you'll be left with some mods highlighted in light-pink with ?'s in their versions. For me, these mods were mostly sub-mods. For example, Natur's Enemy Cast Bars (NECB) had a bunch of components that weren't found individually on the site. Any mods found in this manner can be handled in a variety of ways, all found in the FAQ for WUU.
I've been running it for a couple of days now, and have to say that I'm impressed. My AddOns are being updated to new versions from the web (especially great for Ace2 mods, which seem to update horuly) and nothing has broken in the process. I know people can be hesitant to install software like this, but I took the leap and I've been satisfied. The version I'm using is directly from WUU's site, and is WUU 1.3.262 beta.
If you'd like to download WUU for yourself, use the Sourceforge link earlier in the article, or go to WUU's home site: http://wuu.vagabonds.info/
Let me know what your experiences are like with the software, and if it's something you'd use on a daily/weekly basis.