The Yahoo! mail login page uses some interesting ideas. They hash information on the client-side before attempting to login. They also store retries, and a challenge in hidden fields as well.
I should look into this a bit more. Some of this may be used to make it difficult for scripts to login. Some may be used to make it safer for users of public computers and prevent sensitive information from being cached on the client.
I had an application from another group fail, and lock a DB row that I needed to use. In the investigation, a DBA showed me this code to figure out which rows were locked.
The update will throw an exception, and the max_id of the show_locks table will contain the id of the locked row. This statement can be run again by updating the 1..[max_id] to be [last_id+1]..[max_id].
I haven’t tried it, but I didn’t want to lose the idea either.