Well, no, we don't use SharePoint as a timesheet, cause we got a projectmanagementsystem for that. But SharePoint is used for displaying informations from that and other systems.
I could imagine to create a infopath formular so that daily work could be filled in. One formular per teammember and day.
Another way could be to build a WebPart for creating one list element per each entry typed in the WebPart.
Or you could create a application-page in VS.Net instead of a Webpart and create the listentries from that.