Many resources are now available on the WEB, and the only tricky part is sorting out the scholarly from the not-so-scholarly (I'm trying to be generous here—there's some pretty wacky stuff out there!).
An excellent place to begin any exploration of things medieval is with a site called Labyrinth set up at Georgetown University.
From there you could eventually find an enormously useful site called the On-Line Reference Book for Medieval Studies (ORB). Not only does it have a host of information, secondary material, maps, etc., it also has an extensive library of primary sources in English translation.
Paul Halsall, the force behind the wonderful “Medieval Internet Sourcebook” and related sourcebook sites, has a site dedicated to helping beginners with their medieval research papers, etc. See the Medieval Internet Sourcebook Help Page.
James McNelis has set up a reliable internet page for History of Science on aol.
For recent bibliography on women or gender issues, see the Medieval Feminist Index at Haverford College.
Believe it or not, there is a search engine just for ancient and medieval sites, called Argos. I have not always had the best luck using this– it doesn't always find things that I know are out there, and it often sends me to sites I find irrelevant – but it is certainly worth a try.
Finally, I strongly encourage you to look at the following guides to writing history papers, one from the History Department at the University of Colorado Boulder, and another written by Caroline Schriber of Rhodes College on How to Present an Argument.