Thinker
a. /usr should get its own partition (and should be mounted read only?) to protect it from filesystem failures caused by system crashes.
This was recommended for production systems in the past. This is definitely a bad solution for you nowadays.
b. Have swap on its own hard drive alone with nothing else. (Will having 6GB of swap enhance the performance of the machine or is this just overkill.)
The usable swap partition size is limited to 2 GiB on IA32 (see man mkswap).
c. If you don't have swap on its own drive, make sure that /var and /usr ARE NOT on the same drive with swap. (after reading this, my question is 'ok if this is the case, what is safe to put on the same disk as swap?')
In the first step, don't optimize for speed but for easy administration and upgrades. Suggestions were already presented here. -- A.M.