Gold Open Access
One option for authors who wish to make their work openly accessible is to publish in an open access journal ("gold open access"). Open access can be provided by traditional publishers, who may publish open access as well as subscription-based journals (so-called hybrid open access), or open access publishers such as Public Library of Science (PLOS), who publish only open access journals. An open access journal may or may not charge a publishing fee; open access publishing does not necessarily mean that the author has to pay.
Traditionally, many academic journals levied page charges, long before open access became a possibility. When open access journals do charge processing fees, it is the author's employer or research funder who typically pays the fee, not the individual author, and many journals will waive the fee in cases of financial hardship, or for authors in less-developed countries.
Some institutions have funds to cover the publication fee for their authors (e.g. The Academy of Science of the Czech Republic: http://www.lib.cas.cz/openaccess/) or some countries even have national funds (e.g. Great Britain http://www.rcuk.ac.uk/research/openaccess/). On BUT we have two funds focused on supporting publishing in gold open access.
Beware of predatory publishers! They are just trying to make money on the open access! Check their list on: http://scholarlyoa.com/