If you've had no commercial work experience, it's a little tough to craft a "good developer's" resume I'd say, so I would focus on things you've created while self-learning with demonstrable websites, as well as clearly list all the community sites/forums/lists and whatnot you're involved with and any contributions made.

In a cover letter I'd stress how well you can pick up new technologies and become useful to the client/business very quickly, how passionate you are about keeping up to date with technologies, and somehow indicate you're not a Machiavellian-ego-consumed prima donna that won't shrink when your logic/work is challenged or when the stress hits.

Employers it seems to me these days are asking much more than they would of any other profession i.e. do electricians get asked to trot out a list of sites they've worked on in the past, or are expected to work after hours on open source projects they can demonstrate when they next go to a job? It's tough for recruiters to understand what you're good at, so it becomes a bit of an art to actually letting people know you're good at such-and-such.

I haven't had any problems being self-taught in the development area - once you've got a few engagements under your belt and referees. Getting that first one is the tough bit, if you can prove yourself after that, things get easier and easier.