- Creation date of my own account
- How long have i been online on the last few weeks (or since the beginning if possible)
- Players situation (online/offline)
- My char list
- My Characters infos (lvl, stats, achievement list, guild)
- A tool to compare Achievements between players (it may bring more competitive for us..)
- Top Achievements (same reason as the above)
- Guild infos (number of players, guild icon, average member's lvl, etc..)
- I/O Mailing Service (ingame mail via website... people like me would be able to chat to friends while working)
and a lot more...

this kind of stuff is very very simple to add, and could give a better visibility of your game to people.