DOTGOV2 is a Web crawl of the .gov US government websites, and was used by the TREC Terabyte track 2004-2006, and the Million query track 2007-2008. It can be obtained from the University of Glasgow. The topics and qrels are available from the TREC website:
Indexing the DOTGOV2 collection is easy with Terrier. No terrier.properties are required to be altered from the default created by trec_setup. However, we recommend that indexing is made using the single-pass strategy (trec_terrier.sh -i -j). On a modern machine, indexing usually takes around 24 hours. Using a Hadoop MapReduce job, indexing can be dramatically sped-up.
If you wish URLs in your index, then set the following properties:
trec.collection.class=TRECWebCollection indexer.meta.forward.keys=docno,url indexer.meta.forward.keylens=26,256 ignore.low.idf.terms=false
See the Terrier documentation on Web-based Terrier to see how to build a Web search engine for this collection.