Get top 3 User with most List Items

Hi all,

I have 3 lists and I want to display in a WepPart the top 3 User with most created Items.

Say we have U1, U2 and U2 -user that have created some list items in List A. User U1 has the most list items, so it will appear at first position,... and so on, ok?

Top 3 User for List A

1. U1
2. U2
3. U3

Does someone have done this task alredy? 

thanks for any suggestions

Regards,
Martin