Try Blue Goo! I love this product! Though it is not blue, and not exactly gooey (which I could do without anyways), it does stay true to its "Maximum Strength" claim. Every time I feel sore and my neck or shoulders ache, I smooth some on and within seconds it starts warming. I love putting some on before heading out for a walk!
Purchased from: Wal-Mart near the Pharmacy
Cost: Inexpensive (don't remember how much exactly), there are two kinds.
Warning: Do not apply within 15 minutes from getting in or out of shower. Because your pores are wide open while showering and soon after showering, the heating element can lead to intense burning sensation (I did it!)
Added Perk: To me, it smells like Sweetheart Conversation Hearts, but maybe that's just me ;)