What are some alternatives?
When comparing SharpKeys and xmodmap, you can also consider the following products
Karabiner - Karabiner, previously called KeyRemap4MacBook, is a very powerful keyboard remapper for Mac OS X.
X-Mouse Button Control - XMouse Button Control (XMBC) allows you to create application and window specific profiles.
Key Remapper - Intended for remapping keys, mouse buttons and mouse wheel actions, Key Remapper allows you to:
Key Manager - ATNSOFT Key Manager, Key Remapper, Text Paster
Microsoft keyboard layout creator - Edit the windows keyboard layout.
Simple Disable Key - Do you want to want to disable any key on your keyboard or mouse buttons ?