567020 MySql Database tweaking and optimizing for Joomla website

Hello, this project is for experienced Mysql Database Administrators. My website runs on a Linux CentOs virtual server with 2GB RAM. The website is a Joomla portal with a community extension, a directory and a forum, so there are a lot of queries to Mysql server (5.1). Usually there isn't huge traffic but when about 300 users connect at the same time (like 60 registered + 240 public) the website start slowing down. During that peak time the processor is only working at 5% and there is still 1GB RAM free, so there are lots of available resources. I believe there is something wrong with the database. It needs to be tweaked and optimized for a community website powered by Joomla. Your job is to properly configure the mysql server in order to make the website runs faster under heavy traffic (keeping in mind that it is a very dynamic community website). The attached file is a recent screenshot of the Status of Mysql. Please check it out before bidding. Only bid if you have experience in mysql server administration. Should you have any question, just ask.