Here are some links that I think has useful resources in Oracle Database Development & Administration
http://www.dbasupport.com/ - This is surely one of my favorite sites where there is a wealth of information about oracle developmment and administration. This also has lots of user forums where users can ask questions and share their knowledge with others needing help. This site also has a lot of useful scripts.
http://asktom.orcle.com/ - This is by far the best site that I have visited. This is the first place that I normally visit and look for discussion thread on topics that I need information about. This the official place where you can find answers to almost anything in oracle database. The answers are very useful and is like hearing from the horse mouth :)
http://www.orafaq.com/ - The purpose of this site is to disseminate knowledge amongst the oracle user community. Has a wealth of information categorywise and has some very handy tips.
http://rjh.keybit.net/oracle - This site has a wealth of scripts for every purpose conceivable. Though they have tried to name the scripts according to their purpose, a brief note on what each does, even a one liner would have helped the user community better.
There are many many more. I will keep adding them to the above list.