Is it possible to setup DD-WRT (router firmware family) to send out its IP somewhere? Periodically, or preferably, whenever it just changed?
I am not ready to set up (and pay for) dynamic DNS yet, but I need the IP for incoming traffic.
If any of these options works you've another alternative for the router.
If nothing works then you could configure any of the DDNS Software available for free in one of the computers behind your router.
Not sure about the in-router solution, but as long as you have a computer running behind it, setting up an ip change notifier application is easy. That would monitor its public IP and email you when it changes.
Here's one of many: http://ipchangeinformer.codeplex.com/