Ability to change "signup" to something else (eg "registration") in messages and interface

Would be really nice to have a setting that allowed changing the word "signup" as used in messages, headings and the interface in general (eg signup and cancel buttons) to something else, eg "registrations". At the moment doing this requires a lot of messing around with the theme functions just to change a single word. Let me know if there's some easy way of doing this!