You only have 18hrs use there but if those mysqltuner figures are typical then you have some settings that are way out:
* You only have 2 slow queries out of 4M. That's good.
* Available connections 80 out of 800. That 800 is way too high
* Any memory saving should be redirected to Key Buffer. Ideally you want it to match the 1.2G
* Query Cache is a pointless feature. Best to turn it off.
* You don't seem to be using InnoDB. The 208K is probably just test / background stuff. Disable InnoDB in your my.cnf, restart, check all works, then delete any of the innodb logfiles in the root of your mysql directory
* Lower the wait_timeout
* Join buffer and sort buffer are way too high. Some resources state this works best with as low as 384K. You will need to experiment but start with something like 2M
Other things to consider:
You are using 32-bit and not PAE memory? The 8Gb is not being used effectively. Ideally you want to upgrade to Centos 64-bit version and 64-bit mysql but this is not an easy job.
A later mysql version will be better (for bug fixes and security) but watch that there are now major differences in my.cnf settings with newer versions compared to old. Some statements are deprecated, and some such as disabling innodb, slow log settings require different statements.