IT Pro, Brad McGehee knows SQL, and writes about it frequently. He's even started several websites and blogs dedicated to SQL. A few years ago, he co-authored a paper with me where I discussed fragmentation of the SQL database files (.mdf, .ldf) commonly referred to as external fragmentation, and Brad discussed using DBCC statements to address what is commonly referred to as internal fragmentation. You can read that article here.
On his current SQL blog, SQL Aloha, he ran a survey asking how DBAs handled internal fragmentation. Here are the results:
You can read his full post here.
In addition to the script he links to, there are other good third party options out there to address that internal fragmentation including Idera's SQL defrag manager and Norb Technologies SQL Defrag Studio.
PS: while on the subject, here's another recent article on the subject