but how do you decide which one?
Please understand that there are good, mediocre, and bad journals and publishers in print and online, in subscription and open access venues. Subscription journals have been around longer, so they have a longer history to rely upon when you're choosing a place to submit your manuscript. Here are some tools to help you figure out if an OA journal is trustworthy.
1. Is it listed in the Directory of Open-Access Journals (DOAJ)?
Excellent. This is a non-profit site that lists OA journals that meet their criteria. These criteria don't ensure rigorous peer review, but they do weed out those journals that don't make policies and procedures transparent. Bonus! Submitting to a DOAJ journal means you can apply to the JH Libraries Open Access Promotion Fund for a reimbursement of any fees you incur.
2. Is the publisher on Beall's List of Predatory Publishers?
Run away! Jeff Beall is a librarian at University of Colorado, Denver, who is concerned about the negative affects predatory publishers can have on the scientific endeavor. He outs such publishers on his blog and his list. His criteria for categorizing a publisher as predatory are available.
3. Check with your colleagues.
Have any of your colleagues published in or reviewed for an OA journal recently? What about colleagues who edit for an OA journal? What were their experiences? Which publishers did they work with? Some publishers, like Biomed Central and Hindawi, list authors and reviewers by institution.
4. Follow up on information from the journal/publisher.
Some journals indicate that they're indexed in certain databases, or have faculty from certain universities on their boards. It's easy to list things like this on the web. Follow up on their claims and see if they're really indexed in those databases. A librarian can help you with this kind of detective work.