Now I'm getting older, and really should be using such things, I've given up - except when I'm racing. Years ago it was all part of the warm-up ritual prior to every run. The stuff I used then was 'Dog Oil' which was originally developed by some chap who used it on his racing Greyhounds!
Nowadays I use 'Blue Ease Cream' (Holland & Barratts) for any aches, muscle pulls, knees, joint pains, etc... It's a really penetrating substance containing such peculiar things as Emu Oil, Aloe Vera, Arnica, Witch Hazel, Nettle Extact and goodness knows what besides. I sometimes used it when training in the really cold wet weather before Christmas, when I was still wearing shorts, but not since I acquired my snug running tights!
Prior to a race I'll spend 15 minutes massaging the stuff into my leg muscles to warm and soften them.
Quite regularly after a tough race will do a massage on legs to loosen them up.
Don't need anything special, got given some Adidas muscle recovery cream for Christmas, but most time just use plain old olive oil (seperate from the cooking oil though!). It's absolutely perfect for use and really helps get into the muscles.
Just for comparison, I did a tough XC race and picked up an injury on my right leg. Did a very thorough massage on my right leg to help it out and loose muscles as compared to left leg. Next day right leg was bouncy as anything (though still injured), whilst left leg had pretty severe DOMS. Definitely helps legs after a tough effort.