A contact manager where you can:
-Edit contact information
-Link contacts
-Add extra detail not supported by the online services (eg. Phone#, Address, work, etc.) ** like seen in MSN Live Messenger
-Compare online profile with local profile for contacts

After some basic interface for that sort of thing is done, then maybe you could look into doing more advance things like:

Digsby actually offers only an english spellchecker.

for those of us that use windows media player and the playlists that come with it. I'm not and will never be an iTunes user and i have had winamp and it is nice for the sole reason of flac support but I have not found a way to get the music list to work as well as the one in WMP.

Please ad a option to have separate profiles for each account...

In other clients like Adium and Pidgin to be able to set profiles and status different on each and every account is something that is "essential" for most people running multiple accounts.

There are many people running two or more IM-accounts that is not to be unified...

3-4 Month ago many User in Forum have spoken about Language Support of Digsby and want help with the Localisation into several Languages.

Don't know why Digsby don't have an simple Languagefile what everybody who wants to change into his spoken Language.

The search log feature is pretty useless if you can only search on the day you are looking on. A full log search either of all logs or all logs of the contact that has been currently selected in the log viewer would put a lot of us former trillian and even aim 6 users at home with digsby.

Managing tasks is generally not a fun way to spend your time. We created Remember The Milk so that you no longer have to write your to-do lists on sticky notes, whiteboards, random scraps of paper, or the back of your hand. Remember The Milk makes managing tasks an enjoyable experience.

http://www.rememberthemilk.com/services/api/

Various improvements for how to not ship/install VC++ every time the installer is run.

Let the user deside how to store his password, making "store on server", "store on disc" and "ask on connection" selectable options for every managed account.

The ability to get sms notifications on updates with your myspace, facebook, etc...or even when certain contacts sign on or off.