Architectural Firms' Websites are great, reliable sources of information on an architect or their work. Their sites can give you first-hand information regarding the firm, their projects, publications, awards, news, and lectures, among other things. Use Google or other search engines like Bing! or Dogpile to search for your firms official website. Make sure the site is actually created by your firm by looking for an "About Us" or "Contact Us" page, or by looking for contact or copyright information somewhere on the site (possibly listed on the bottom).
Here are some other reliable, authoritative web sites about landscape architecture: