<p>Are there any known methods of finding peers without using a dedicated central server?</p>

<p>ie: If I have peers which are disconnecting and reconnecting to the internet but getting a new IP address each time, and I want to connect to them without setting up a dedicated server to register with.</p>

<p>I was thinking about using peers email address to send a manifest of connected peers periodically, with some sort of timecode, negating the need for a dedicated server.  This would be a fallback if none of the peers could be connected to after trying all the previously known peer addresses.  But existing models of finding peers would be preferable.</p>

Three ways, off the top of my head, though you're always going to need some central server to start the connection unless you went with option 3.
Central server that maintains known list of peers, with keep-alive.
One or more central servers that maintain some common resource peers can use to discover one another, but once connected no longer need the central server as long as the peer remains connected (something like BitTorrent); can chain peered connections as well.
Port/IP scanning (
strongly not recommended
).
In your example, you'd still have some kind of central server where the peers would be registered; the protocol is the only difference.