User Interface Design for Programmers by Joel Spolsky is a really good book for Interface design when you are not use to thinking about how the users are going to use your program.

Great book for anyone given how he breaks down everything.

The 19 Deadly Sins of Software Security is a book that I would say is almost a necessity for any collection. It helps to show some of the issues that the different programming languages have and how to fix the problem.
Hacking : The Art of Exploitation is another great book that I would say you should have to bring more knowledge about how to prevent and write better code.
Outside of that I own a ton of Programming/Application design methodology books.