Online journals and news
Compilations, portals, and special sources
Journals
Newsletters
Other ....not agriculture but possibly of interest (health, etc.)

Online journals and news:
Science in Africa: online science magazine
Genome News Network: news and other helpful genome-related info, including a guide to sequenced genomes

Compilations, portals, and special sources:
AGORA http://www.aginternetwork.org/en/index.php. Access to Global Online Research in Agriculture. Free to qualifying not-for-profit institutions in eligible developing countries. Access to over 500 journals from major scientific publishers in the fields of food, agriculture, environmental science and related social sciences.

JStor http://www.jstor.org/ is a scholarly journals archive

The Essential Electronic Agriculture Library http://www.teeal.org/. TEEAL is a full-text and bibliographic CD-ROM library of over 140 of the world's most important scientific journals in the field of agriculture.  It is available well below cost to over 100 of the lowest-income food deficit countries, as listed in the World Bank's 1998-9 World Development Report.

Science Direct http://www.info.sciencedirect.com/. Source of many journals, free access to tables of contents, options to buy per article or per subscription set.

Journals:
Public Library of Science (PLOS) http://biology.plosjournals.org. A peer-reviewed, open access journal
Plant Molecular Biology Reporter. Open access up to most recent year
Crop Science (subscription) http://crop.scijournals.org
Journal of Molecular Biology (subscription)
Crop Science (subscription)
PNAS (subscription)
Theor Appl Genet (subscription)
Science (subscription)
Nature (subscription)

Newsletters:
Sol Newsletters (from the Solanaceae Genomic Network, SGN).
Maize Newsletter

Other....
The Health InterNetwork Access to Research Initiative (HINARI) provides free or very low cost online access to the major journals in biomedical and related social sciences to local, non-profit institutions in developing countries. http://www.healthinternetwork.org/src/eligibility.php