For emails, I sort as I go so that my inbox only contains items that still need attention. Gmail is a lovely way to do this.
Folders/labels that I would use would be:
Inbox (items that still need replies)
Show #1 - Resolved
Show #1 - Reference (emails that require no reply)
Show #1 - To do (You've replied but still have stuff to do)
Show #2 - Resolved
Show #2 - Reference
Show #2 - To do
Personal
As soon as you respond to an email, file & archive the entire thread so that your inbox ONLY ever contains things that need a reply. Likewise, as soon as you finish a to-do item, file and archive that as well. It's much less daunting to open up your inbox and see just a short little list. This way, things that you need to do are filed neatly. Gmail makes this all really easy - you can label as you go. If you turn on keyboard shortcuts you can even label quickly by hitting . while you're viewing a message. Personal stuff gets filed separately from the work stuff - this is especially important if you're using one email account for everything.
If you keep a laptop handy in the rehearsal room you can email yourself to-dos as you go, provided that you're consistent with it. Every to do, send yourself an email using the item as the subject line. If you're handy with filters, you can set up your email so that if the subject line starts with "to-do" it will get filtered over to your to-do list automatically. (Alternately, using Gmail you can set it up so that emails sent to yourusername.showname_todo@gmail.com get labelled & archived automatically.)