I run dnsmasq on my machines, for example, and its primary purpose is to alter DNS resolution - my nameserver is set to localhost, and my dnsmasq configuration sets which DNS servers to use for what top level domains etc., and routes *.local to a flat file on my home server, for example.
Dnsmasq itself isn't suited to avoid SOPA, but it's a good proof of concept for a small dns server that mediates the lookups based on rules, but defer to "regular DNS" for everything else. There are tons of simple DNS servers out there that can easily be modified to do detect likely SOPA blocked domains and use whatever mechanisms to resolve it through non-US servers (even if your upstream ISP gets forced to filter DNS).
Worst case? Distribute zone files of blocked domains as torrents automatically, or hide lookups in otherwise innocuous looking traffic.
If they IP block the sites, the same mechanism can be used to serve up lists of addresses of proxies instead of the real sites.
The system just needs to be faster than the SOPA proponents manage to send their extortion letters to ISPs.
The beauty is that if/when mechanisms like this start becoming commonplace, the cat is out of the bag - they'll never regain control.
IM unfamiliar with the bill, but given SOPA's wording, could it be that the whole of addons.mozilla.org, or even mozilla.org end up banned?
> At best, it would be distributed underground
If it were to happen, I envision a world where Aunt Jackie will ask little nephew Steve to enable her the full internets because she can't watch some photos on Flickr anymore, just like she could not install the Flash ten years ago. Steve will simply be asked to provide a piece of software to bootstrap, which if banned from the internets, will be distributed on underground network channels then diffused on a local scale through sneakernet.
It looks awfully like the BBS and early Internet in the '90s, with those warez sources like IRC DDC bots, and a select few having access to such sources and able to distribute pirated games on high-price CD-Rs.