The German National Library (Deutsche Bibliothek) provides an English version of portions of their website.  There are links that imply they have a document delivery service, but I've not yet found any pages in English that explain the terms.  It may be that it is necessary to use one of the three delivery systems listed below.

GBV Direct -- no longer can provide documents to overseas libraries! . Here is their notice . However, libraries may still find this link (GBV Databases) useful in confirming titles and volumes held in German librariesThe GBV site includes a linked list of GBV libraries.

SUBITO (English version) document delivery service allows a user to search one of the three major bibliographic databases in the German Library.  This network includes several German libraries. Use ADI (Aufsatxdienst International) to search for journal articles 1992 forward; ZDB (Zeitschriftendatenbank) for journal titles; a monograph database for books, conference proceedings and dissertaitons. Several libraries in the Subito system are delivering articles in PDF format. This appears to be a commercial site. UPDATE: Subito is currently restricted from providing documents overseas! Here is their explanation.

German North American Recources Project one of the working projects of the AAU/ARL Global Resources Network. Their page of web resources gives some links that might be useful. It is this group that initiated GBV Direkt.

See also the Meeting Summary AAU/ARL German Resources Project: Access to Information Resources Through ARL-German Collaboration held at The Thomas Jefferson Building Library of Congress Washington, June 25, 1998, although this was done before the moratorium on sending copies to foreign countries.

Fuch, Heinz. "German Interlending and Document Delivery in the Nineties" from  Interlending and document supply: resource sharing possibilities and barrier, edited by Sarah Gould and Dave Jojnson.  IFLA 1998 (ISBN 0953243915) pp.45-56