Jeremy Zawodny points out that Gmail’s spam filtering has gotten pretty good. (Using Gmail as My Spam Filter (by Jeremy Zawodny)) Combine its spam filtering with the ability to download your Gmail messages into an ordinary mail client (like Thunderbird) via POP, and what you’ve got is a pretty kick-ass mail server. You can use a client-side interface when you’re at your computer; everywhere else, you can still get to all your mail via the Gmail web interface. (One of the comments on Jeremy’s post points out that Gmail even archives mail you send via SMTP, provided that you use the Gmail SMTP server. Pretty slick!)
My own mail solution is a bit different. I use Thunderbird to access my mail accounts on birdhouse via IMAP. When I’m on the road, I can use webmail to check my messages (if I’m on a secure connection), or I can set up a secure ssh connection to the birdhouse server and use Pine to read my inbox — and all my IMAP folders, too. The big advantage that Pine has over web interfaces (even really slick ones like Gmail) is that it’s incredibly fast. I can delete and archive mail much, must faster with Pine’s keyboard commands than I can in any graphical interface. And, as a side note, birdhouse’s spam filtering (based on SpamAssassin) is very effective, and only lets a handful (5-10) spam messages through per day.