E-mail forwarding for a change in e-mail address?

Soon I may have to cancel my current ISP (AOL) to switch to a free e-mail account such as Gmail, but I'm concerned that after having to switch my e-mail address for so many things (several dozen), there will likely be a few that I end up missing, and that eventually a few e-mails will be sent to my old, then-defunct AOL e-mail address.

Is there possibly anything at all, such as an e-mail forwarding application or program or whatever, that could somehow re-direct such e-mails going to my old, then-defunct AOL e-mail address to my new one?  It would seem to be impossible to me, but I'm hoping that I'm wrong.

Any helpful replies would be very much appreciated - THANKS.