A web portal or gateway is a classified collection of links to other web pages.
Examples:
Maria Pantelia's Electronic Resources for Classicists (http://www.tlg.uci.edu/index/resources.html) - one of the most comprehensive portals for Classics that also contains links to several other portal.
New Testament Gateway (http://ntgateway.com) - excellent portal for New Testament Studies and related fields.
Resource Pages for Biblical Studies (http://torreys.org/bible) - contains int. al. links to sources about the social world of the ancient Mediterranean.
Rutgers University Virtual Religion Index (http://virtualreligion.net/vri/) - offers a large collection of links to Internet sources on religious topics, including Ancient Near Eastern, Greek and Roman religions, as well as the Hebrew Bible and the New Testament.
ABZU (http://www.etana.org/abzubib) - contains a large collection of sources (including the complete texts of books) on the Ancient Near East.
Ancient Near East.Net (http://www.ancientneareast.net) - contains a collection of sources and links on the ANE for researchers and laypersons.
New Pauly Online (Brill’'s New Pauly) (Stellenbosch University library > Databases > N >) - up to date and authoritative encyclopedia on the ancient world.
Thesaurus linguae graecae (TLG) (Stellenbosch University library > Databases > T >) - almost complete database of ancient Greek texts up to Byzantine period; dictionaries; complex searches.
Packard Humanities Institute (PHI) Latin texts (http://latin.packhum.org) - classical Latin texts; includes Word search and Concordance.
Suda Online (http://www.stoa.org/sol/) - Byzantine encyclopedia on ancient authors and topics; translation and Greek; search on topics.
There are several websites with bibliographical information about specific ancient authors.
The more general sources are the following:
L'Année philologique (http://www.annee-philologique.com/aph) - an Internet version of the most important bibliographical aid for Classical Studies. Admission is only by subscription, but it is free through the Stellenbosch University Library's website (http://library.sun.ac.za//index.htm). Follow the link to Databases and choose L'Année philologique (alphabetised under A).
Tables of Contents of Journals of Interest to Classicists(http://www.chass.utoronto.ca/amphoras/tocs.html) - gives a valuable survey of the table of contents of classical and related journals.
Propylaeum Virtual library (http://www.propylaeum.de/) - books on ancient studies in German libraries.
American Schools of Oriental Research Publications (http://www.asor.org/pubs/index.html) - with links to the journals Bulletin of the American Schools of Oriental Research, Journal of Cuneiform Studies and Near Eastern Archaeology.
Brynn Mawr Classical Review (http://bmcr.brynmawr.edu/) - reviews of books on Classics. One may search the website or subscribe to receive reviews by e-mail.
Biblical Archaeology Society (http://www.bib-arch.org/index.asp) - contains links to the semi-scientific journals Archaeology Odyssey, Biblical Archaeology Review and Bible Review.
Metropolitan Museum of Art (New York) (http://www.metmuseum.org) - links to the ancient culture collections, with the possibility to search for online subjects.