Find alternatives to the software you’re using

I use a lot of different software, and I am always looking to try out similar software to see if I can find something better. However, finding an alternative to, let’s say Sony eBook Library, isn’t always as easy as one would like.
 
Enter AlternativeTo.net. A simple search for eBook Library nets us five pages of programs (15 programs to a page).
 
One problem I can see right now, is that it doesn’t always display relevant hits. Still, it’s a lot better than the hit-and-miss that you get if you don’t try a lookup.