Open access journals are scholarly journals that are available to the reader "without financial or other barrier other than access to the internet itself." Some are subsidized, and some require payment on behalf of the author.

Here are some of the common sites which list open access journals:

Philippine Journals Online
http://www.philjol.info
Philippine Journals Online is a database of journals published in Philippines, covering the full range of academic disciplines. The objective of PhilJOL is to give greater visibility to the participating journals, and to the research they convey.

UP Diliman Journals Online
http://journals.upd.edu.ph/
The University of the Philippines (UP) Diliman Journals Online is a free online service exclusively offered to UP Diliman journals. It aims to gather all the UP Diliman journals in a single repository and widen their dissemination and visibility online.

JournalSeek
http://journalseek.net
Largest completely categorized database of freely available journal information available on the internet. The database presently contains 92673 titles.

Public Library of Science
http://www.plosjournals.org
A nonprofit organization committed to making the world’s scientific and medical literature freely available online, without restrictions on use or further distribution, free from private or government control.

Scitation
http://scitation.aip.org
Re-launch of the Online Journal Publishing Service (OJPS), a leader in online sci-tech publishing and journal hosting since 1996.

Directory of Open Access Journals
http://www.doaj.org
Covers free, full text, quality controlled scientific and scholarly journals.There are now 2747 journals in the directory. Currently 829 journals are searchable at article level. As of today 139702 articles are included in the DOAJ service.

CiteSeer
http://citeseer.ist.psu.edu
A scientific literature digital library and search engine that focuses primarily on the literature in computer and information science. CiteSeer was the first digital library and search engine to provide automated citation indexing and citation linking using the method of autonomous citation indexing.

Project Muse
http://muse.jhu.edu
Unique collaboration between libraries and publishers providing 100% full-text, affordable and user-friendly online access to over 300 high quality humanities, arts, and social sciences journals from 60 scholarly publishers.

Highwire Press
http://highwire.stanford.edu
Hosts the largest repository of high impact, peer-reviewed content, with 1053 journals and 4,344,778 full text articles from over 130 scholarly publishers. HighWire-hosted publishers have collectively made 1,698,186 articles free. Highwire produces 71 of the 200 most-frequently-cited journals.

Google Scholar
http://scholar.google.com
Provides a simple way to broadly search for scholarly literature. From one place, you can search across many disciplines and sources: peer-reviewed papers, theses, books, abstracts and articles, from academic publishers, professional societies, preprint repositories, universities and other scholarly organizations.

Scirus
http://www.scirus.com
Most comprehensive science-specific search engine on the Internet. Driven by the latest search engine technology, Scirus searches over 415 million science-specific Web pages.

OpenJ-Gate
http://www.openj-gate.com
Electronic gateway to global journal literature in open access domain. Open J-Gate provides seamless access to millions of journal articles available online. Open J-Gate is also a database of journal literature, indexed from 3000+ open access journals, with links to full text at publisher sites.

AGORA - Access to Global Online Research in Agriculture
http://www.aginternetwork.org/en/index.php
Enables developing countries to gain access to an outstanding digital library collection in the fields of food, agriculture, environmental science and related social sciences.

IngentaConnect
http://www.ingentaconnect.com