Here is a collection of links to various resources for information on Down Syndrome or other associations that can help.
http://www.downsed.org/ is a site from the UK that has great on-line resources. Articles on speech, language, dentistry, etc are all available from the information network portion of the website.
http://www.down-syndrome.info/topics/recommended/families/ is a recommended reaading list for families. I found many of the articles to be extremely useful.
http://disabilityisnatural.com/ is a wonderful site with a lot of information about advocacy and general information.
http://davehingsburger.blogspot.com/ is a great disability blog.