The latest edition of SPARC E-News contains an article, SPARC Europe on Open Access by David Prosser, outlining a proposal that I've mentioned before and support wholeheartedly.
This involves journals offering the option for authors (or rather, their institutions or funding bodies) to cover the costs of publication and peer review, in exchange for the publisher making the paper freely accessible. This preserves the impact factor and prestige that comes from being published in a leading journal, while adding the increased visibility and impact of open access.
One point which needs further discussion is the price which authors should have to pay. The publisher may want to charge a higher price for making a high-quality paper open access, due to the loss of sales it would normally generate. On the other hand, the author may be able to negotiate a lower price for a high-quality paper, as the journal needs to maintain a good reputation. If the price is to be negotiable in this way, it may lead to papers being published unfairly based on the profit motives of the publishers and wealth of the authors.
Another point which isn't addressed is the option for authors to pay the open access fee to 'renationalise' their previously published papers. However, there is a danger that this could undermine ongoing efforts to make all content older than six months freely available.
It would be good if a negotiating committee could be set up to sort out the details of this proposal with the leading publishers as soon as possible.