The Windows version of 11g is now available for download. If you visit the main database download page you can agree to the terms and conditions and download the software:
http://www.oracle.com/technology/software/products/database/index.html?rssid=rss_otn_soft
For OLAP, Data Mining and Warehouse Builder you will need to download the database, client and Examples zip files. Look for the See All link on that page:
Microsoft Windows (1.7 GB) | See All (Including Client, Examples, Gateways, and Clusterware)
http://www.oracle.com/technology/software/products/database/oracle11g/111060_win32soft.html
All the documentation to support 11g is also available via OTN:
http://www.oracle.com/technology/documentation/database11gR1.html