This is a small C# application I wrote which converts between decimal, binary, and hexadecimal. You can input the numbers however you want, and it will automatically detect what base your input is given in (using prefixes such as 0x and 0b, or it makes assumptions based on whether or not you have inputted any letters). If the application window is open, the input is given in a text box, if the window is hidden, then the application monitors your clipboard for changes. If you copy a number that can be converted into your clipboard, then the application will convert it for you and notify you of the results in the corner of the screen.
I'm not very creative when it comes to icons so I stole the Cygwin icon, it looks like a black C with a green arrow in the middle. Sorry.