It's an amazing site whose objective is to make the scientific literature available for free to the scientific community. Of course, you will have to pay if your article is accepted in their journals. The following are the core principles of PLoS: (Modified from their website)
- Open access.
- Excellence.
- Scientific integrity.
- Breadth.
- Cooperation.
- Financial fairness.
- Community engagement.
- Internationalism.
- Science as a public resource.
1. PLoS One
2. PLoS Biology
3. PLoS Medicine
4. PLoS Computational Biology
5. PLoS Genetics
6. PLoS Pathogens
7. PLoS Neglected Tropical Diseases
Their web site is user friendly and have various features such as news, journal information etc. Visit the website and browse through the different subject areas. The users can go to this webpage for more friendly version http://www.plosone.org/static/users.action
If you need more help in using the site follow this link
http://www.plosone.org/static/help.action