Re: More powerful maps, multi-person SMS lead new iPhone features
You can set this up entirely in GMail - it can check up to five other e-mail accounts and pull everything into GMail. You can set up combinations of filters and labels in GMail if you need to know which account a particular e-mail came from (ie, create a label called "work", and a filter that applies the "work" label to any e-mail that comes from your work account - GMail will then present a Work folder that will contain everything that comes from that account). GMail will also let you reply to e-mails using either your GMail address, or the address the original message was sent to.
GMail effectively becomes your "universal inbox". It has a great SPAM filter, so that becomes almost entirely a non-issue (occasionally, something does get through, and there are the occasional "false positives"), and if you use IMAP on all of your devices, you'll never have to sort through the same unread messages in multiple e-mail clients - once you read something on one device, it won't show up as unread anywhere else.
I got this working about a month ago, and it's really streamlined e-mail for me. Combine it with the recent release of NetNewsWire as freeware, with its ability to sync across multiple devices and great web/mobile RSS access, and you get the same streamlining with RSS - no more reading articles at work, then coming home and having to remember what you have already read. With the new WebClips on the iPhone, I now have an icon that takes me directly to the mobile reader, and it only presents things I've left unread or new items since I last checked. You could accomplish the same thing with the Google reader, but I prefer having a desktop RSS reader when at my Mac.