We are using the Timesheet Reports and Gadgets Add-On for JIRA. It’s available on the Atlassian Marketplace under a BSD licence, but it’s not free.
On our JIRA 5.0.x server, it was accessible from the Projects tab > Summary page > Reports drop-down list > Time Sheet Report item.
After upgrading to JIRA 6.x, it was accessible from Projects tab > Summary page > Reports section heading > Time Sheet Report.
One tip for the timesheet report is that you don’t need to give a beginning and end date for the report: it defaults to the past week. So you can bookmark the report and come back later for a report of the last week.