I've been thinking about some ideas for Gtalk, instant messenger from Google.
In case somebody have the time to implement it on Pidgin or some other not official client here I present the ideas:
Groups of contacts are not a new feature, but rating those groups or maybe even individually each contact, yes it is. Sometimes you don't want to speak with people for several reasons: commercials, personals, academics, etc.
What if you don't want to be seen depending on what context are you working? If you can make categories for your contacts, then you can define wich categories can see you depending on what "status" or context you are. For instance, on weekends and holidays, you don't want to see most of your customers, or co-workers, then automatically on Friday at 5:30 PM, you are unavailable for them. For the same reason you on office time, or on some situations don't want to be disturb by your students o by your family or by friends, because you use the instant messenger also for work, and instead of having multiple accounts, you want the same account to perform differently according to what role you are.