Stretch, ice, heat, massage, ibuprofen & light activity
There is no real cure for Delayed Onset Muscle Soreness (DOMS) and some of these suggestions are unproven (while some have been proven not to work) there is some science and lots of anecdotal evidence that these things will help.
Stretching after your workout is a common practice which has many benefits. Some people report that it helps reduce DOMS but unfortunately the science says that it doesn't really.
Heating and icing help facilitate bringing blood into and pushing blood out of the sore area which help recovery. Ice/heat can have a soothing affect too but that depends on the person (personally I hate the feeling of icing).
Lightly massaging the sore muscles has also been report to help reduce DOMS but again there is no proof to back it up. I think it feels good though so it may just be psychological.
ibuprofen is an anti-inflammatory and pain reliever. I think this benefits of this are obvious, but I will say to be careful to understand the health risks as you should do when ingesting any kind of chemical.
Doing an Active Recovery (light activity) immediately after your workout will help reduce muscle lactate levels. Continuing to do active recovery activity in the days after your workout is a good way to keep the blood flow going to the sore muscles and prevent the muscles from tightening.