1) Rest/Active Recovery - Getting plenty of sleep and resting your body may be the most effective treatment. In addition, active recovery, which is light exercise during the recovery phase can stimulate blood flow to the muscles to help reduce muscle pain. Active recovery can include swimming, or a light jog.
2) Hydration - Drinking plenty of water can help flush out toxins from your body and prevent dehydration, which can make muscle soreness even more painful. While there is no consensus on how much water you should drink, somewhere around 1/2 your body weight in ounces of water per day is a good starting point.
3) Pre & Post-Workout Nutrition - Consuming a 2:1 ratio of carbs to protein either before, or after a workout, or both, may help reduce the severity of muscle soreness. (See: The Fit 5 - Pre & Post Workout Nutrition)
4) Topical Creams - creams like Ben Gay and IcyHot provide the perception of pain relief, but have no effects on the underlying muscle.
5) NSAIDS - nonsteroidal anti-inflammatory drugs like Advil and Alleve can help relieve the discomfort of muscle soreness. It's not advisable to use NSAIDS on a consistent basis, but rather for an acute bout of soreness.
Other treatments include ice, cold baths, Epsom salt baths, massage and gentle stretching, but the effectiveness of these methods for speeding up recovery is questionable.
The same variables apply to running where fitness level is particularly important. For example, some elite marathoners run 100+ miles per week and need almost no rest between runs. On the other hand, a weekend warrior may attempt to run 20 miles in a week, or change up the stimulus with hill running, which could create intense soreness and require longer recovery times.