To find open access journals in your discipline, search the Directory of Open Access Journals, or ask your liaison librarian to help you identify titles.
To evaluate the quality of an OA journal, use the Open Access Journal Quality Indicators created at Grand Valley State University.
Unethical publishers are sometimes called "predatory publishers." There is a growing industry made of "publishers" that operate in a couple of ways. Some contact new authors (particularly graduate/undergraduate student authors) and "offer" to publish their work in exchange for the copyright. They typically post the work on amazon or other sites and print a copy on demand for anyone who orders it (usually almost no one). Others create a fake journal which is not peer-reviewed or edited, and they charge authors for publishing in said journal.
If you receive a "too good to be true" communication about your scholarship, please be skeptical. Librarians are happy to help investigate the legitimacy of such communications.