OSG is very powerful, with well designed API, and as such does a great job of rendering games or similar applications. It's not very friendly to beginners due to being very general and making use of advanced design patterns, but that's the price for a professional engine. I've encountered a few bugs here and there, but overall my experience is very positive and I now prefer OSG over other engines such as Ogre3D.
There's no competition if you aim to create a beautiful, professionally looking document. A must if you're writing a book, thesis, or anything with math equations. Nowadays there are web services that make using LaTeX easy, right in your browser, so there really is no excuse for the ugly MS Word documents anymore!
Pelican served me very well, I was able to create quite a complex multilingual blog with it. It's easy to write your own extensions if any functionality is missing, plus there is already a number of existing plugins out there. I had issues with hosting the site and it's source in the same repo at GitHub, but that's easily solvable by hosting the source in a separate one.
It simply works, plays everything I throw at it, can make screenshots, step by frames, play streams and more. I'm giving 4/5 because it's a bit slower to start than some other players and doesn't blow my mind with anything extra awesome, but it really is a very good player.
I'm using this lib for my new game and it's awesome. It has all you need for 2D games, plus it is very, very easy to pick up thanks to the nice API and documentation. I chose it over SDL because SFML has a nicer way of handling sprite transformations.
Addictive, but requires a great skill, and can also get frustrating. I got stuck at some very hard levels. What I like are the player ghosts - you can even race against the current world record on each track! I'm leaving out one star because the graphics and sound aren't great.
V