Currently, the easiest way to manage multiple email accounts at the same time is by using a standalone IMAP client. Five accounts in the sidebar that I can access with a single click, with Unified Inbox at the top!
Gmail's web interface only lets you access one email account at a time. You could have delegated accounts, but they open in a separate tab, and the whole concept of delegation only works for Gmail accounts anyway. Or you could forward everything to your Gmail account and call it a day, but some employers might have a problem with that, especially in light of Google's apparently comfy relationship with No Such Agency.
Personally, I use my Gmail address to subscribe to public newsgroups, but I wouldn't let anything private ever touch a Google server. With a standalone IMAP client, it's very easy to maintain this kind of separation without having to suffer any noticeable inconvenience.