Yahoo’s Dante Alighieri directory page:
http://dir.yahoo.com/Arts/Humanities/Literature/Authors/Poets/Alighieri__Dante__1265_1321_/
Digital Dante Project (From the Institute of Learning Technologies (ILT)): 
Dante’s Realm a really good website about Dante’s Comedy, with comments on each Canto and also an image gallery.
Dante Online an interesting website with info, texts, related interviews, bibliographies and news. Available both in Italian and in English.
From the "Dante and others" website a prose translation of the Commedia written in English and provided with a name index and hyperlinked notes to each canto and also a translation of the Vita Nuova available on a single page here. Very useful if you can’t read in Italian.
A new English translation of the Commedia and a selection of Dante’s poems from various works (among which the Vita Nuova, the Convivio, the Eclogues, etc.) translated into English. A short introduction to the work is also given.
An online edition of the Commedia entirely in Italian with detailed comments by authorative scholars.
"Dante’s Inferno", a very well done site about the first book of the Commedia.
Very detailed site about Beatrice and her influence on Dante’s life and work. The site is entirely in Italian language. Click here.
"Concordances": this site is a sort of text search engine working on Dante’s Commedia, both in Italian and in English. It may help you if you’re looking for a specific quotation or name and you don’t know where to find it.
Dante Studies: a comprehensive bibliographical guide about everything referring to Dante available on the web and outside it.
PDP: the Princeton Dante Project is yet another excellent webguide to various aspects of Dante’s work and times.
Inspired by Dante is a nice art gallery with works by Jennifer Strange, based mainly on episodes of the Inferno.
You want to have some fun while learning Dante’s structure of Hell, Purgatory and Heaven? Take Dante’s Inferno Test and see where Dante would put you.
If you understand Italian, you can listen to cantos from the Commedia read by famous Italian actor Vittorio Gassman. Available here (please note the site is entirely in Italian).
The Project Manuzio Home Page (a lot of Italian literary texts available for download):
English home page
Italian home page
The Project Gutenberg home page (a lot of worldwide texts available for download):
http://www.promo.net/pg/
The Project Libellus home page (a lot of Latin texts available for download):
click here
The Latin Library: a lot of Latin texts from various authors, from the Classics to modern ones.
The Ring of Books link page, from where you can follow blind links to other sites about literature and related topics:
click here.