Here's some websites you may find useful:
www.winepage.de. An English-language website run by Dr. Peter Ruhrberg. Very useful.
www.vdp.de. The website of the Verband Deutscher Prädikatsweingüter, with an English section and links to many top wine-maker's websites.
www.bernkasteler-ring.de. The website of the Bernkasteler Ring, the oldest association of quality winegrowers. German language only, unfortunately. Again, with links to many top winemaker's websites.
www.germanwine.net. The website of Rudi Weist, the US importers of several fine estates, with useful but often wildy over-optimistic vintage reports.
www.skurnikwines.com. The website of another US importer of German wines, with notes and vintage reports written in a rather strange, very wordy and highly idiosyncratic style by Terry Thiese. Interesting nonetheless.
www.timelesswines.com. Another US importer of fine German wines. No vintage reports as far as I can see, but useful for those in America.
www.germanwinesdirect.org The only place on the internet for info on buying wine direct from the winemaker...
Here's some books I've found useful:
The Wines Of Germany, by Frank Schoonmaker and Peter M. F. Sichel
First written in 1956 by Frank Schoonmaker, the massive changes to the German wine law in 1971 made this book obsolete, but it was successfully revised in 1983 by Peter Sichel, and is written in beautiful English, despite the fact that both the authors were American. Many of the recommendations in this book still hold true today, which is quite an acheivement. This book has been out of print for many years, but is still available secondhand from Amazon. I take it with me whenever I visit the wine regions, and am now on my fourth copy...
The World Atlas Of Wine, by Hugh Johnson and Jancis Robinson.
Good text allied to stunning high detail maps make this book a winner. The maps even show many of the small roads through the vineyards, and athough it's probably illegal I take a photocopy of the relevant maps whenever I visit the wine regions, it's THAT useful.
Finally, here's a link to an English translation of the poem Mosella by Roman poet Ausonius:
www.archive.org/details/deciausonius01ausouoft