I also played around with web sites, mostly Wiki and alike:

• SEO Wiki
  A Wiki on Search Engine Optimization. I could not believe how quick I went up in Google. Easy stuff. The German SEO site is on page 1, the English site is on page 2.
• E-Commerce Wiki
  A Wiki on E-Commerce strategies. Also available as the German E-Commerce Wiki.
• Data Warehousing Wiki
  A wiki on data warehousing. Auch auf deutsch verfügbar! Now, also a blog on the topic.
• Open Source Software and Strategies Wiki
  Work in progress. A wiki on Open Source. Auch auf deutsch verfügbar!