This tip is primarily about a nice new tech tool, but non-Gmail users can skip down to general principles that should be helpful with any list of things to deal with.
Google Mail now offers a feature called "Priority Inbox" which allows you to have three tiers in your email inbox with automatically-detected (and adjustable) important messages sorted into the top section. I've given it a try and find it does help me prioritize my time better.
The default tiers are "Important," "Starred," and "Everything Else," but since I don't use stars that much and I do have an email-intensive volunteer project, I've taken advantage of the customization options to change the middle section to contain all the things in my inbox which have a particular label identifying it as part of that project. If you use Gmail, go under Settings and check out the options in the Priority Inbox tab; I think you'll like it.
Beyond this specific tool, though, there are some great principles at work here.
1. Clump stuff together.
It's easier to tackle similar items than dissimilar items. Put all those "add to calendar" notes in one pile and all those "bills to confirm and pay" in another. You'll complete the tasks faster if you don't have to keep switching modes from calendar to bill pay.
2. Isolate large projects.
This is the same principle, but has extra benefits with longer, more focused work. Being able to close off the "hot but not necessarily strategic" and the "noisy but low priority" from your view when you are doing a session of work on a project is a huge help in making effective use of that time. Whether it's the ability to sit at your desk with only that project folder in front of you and no other papers nagging at the corners of your vision or using a software feature like OmniFocus' Focused view, build yourself clear thinking space.
3. Enjoy your finite attention.
You are going to receive more demands upon your attention than you have time for. You'll get too much email and by all kinds of methods online and off you'll find out about too many cool links/shows/books/hobbies/ideas for anyone to explore in one lifetime. Embrace this.
If you're walking on the beach, trying to pick up every shell you see will impair, not increase, your enjoyment. Pass things by without anxiety. And by that I mean delete, archive, recycle, unsubscribe. Don't let things pile up in the hope you can get to them someday; let the chaff go. Heck, let some of the grain go; there will be more good stuff to capture your attention tomorrow.
Let "Everything Else" beyond "Important" and your big projects offer itself for your consideration and ruthlessly respond to almost none of it. Either it matters now or it belongs to a project (active or inactive or new) or it belongs in your "Someday/Maybe" cool storage for later consideration or else you don't need it.
When feeling overwhelmed, check to see if you're keeping too much stuff under consideration that you should just drop and move on from. Picture the intangible as physical and the silliness of what you've been asking yourself to do will often give you the lift you need to take care of yourself. If those 2,327 things in your inbox were pieces of paper you were trying to hold in your hands, of course you'd be stressed! Stop asking yourself to do that! Decide and do or let it go.