This CAML tool from Carlos Segura is well worth a look. Based on the KISS principle, this tool makes creating complex CAML queries simple by allowing you to use an SQL syntax to define your queries.
By entering the query you are then able to switch tabs to see the CAML...
This tool takes the headache out of working out your <And>s and <Or>s, allowing you to use parenthesis for operator preference. It has certainly saved me some time...thanks Carlos!