Liz you can also subscribe to an email performance report and set it to automatically send the excel spreadsheet to your inbox as frequently as needed. Very helpful, especially when you are asked for it frequently!
There are two export the data to Excel:
Report > Excel
Email Performance > Export
The Excel spreadsheet looks like this:
Remember to look at your setup
In particular which emails you are reporting against and the time period. I find it useful to set the time period to one year. If you leave the report in the default setting of 'last 7 days', when you check the report next month it says 0 emails opened/sent/delivered, because it is only looking at the performance over 7 days, which is probably not what you are looking for.
Also it may be worth setting up 2 reports for Email Performance.
1) report where you monitor the emails for one campaign and/or month
2) report where you measure all the emails from similar campaigns or for an entire year
Hope this helps,