"A kiss is a lovely trick designed by nature to stop speech when words become superfluous." - Ingrid Bergman
Elephant Journal has a great article by Wendy Strgar of Good Clean Love about (my favorite topic) the mindfulness practice that is kissing: http://www.elephantjournal.com/2010/06/the-art-and-science-of-a-kiss/
And, here is an excerpt (since I couldn't clip just one enticing quote...):
"Kissing is the building block of intimacy. Done with intention and passion, the kiss is the most profound of all our communication devices and the pathway to sustaining loving relationships.
"Think back to some of the hottest sex you ever had and you might remember that you were fully clothed and that the sex happened entirely between the lips – and what lips we have for the job… It turns out when you study philematology that human lips have the slimmest layer of skin on the body and are among the most densely populated with sensory neurons of any bodily region, more so than fingertips or even genitalia. That isn’t the only place where the human body is wired to kiss. Half of our cranial neurons influence the kiss by releasing a cascade of neural messages and chemicals, which create the intense euphoric sensations and the vital signals about the sexual/mating potential.
"And, no—it’s not just in your mind: everyone has a racing heart and finds him or herself breathless and maybe even a bit sweaty. It turns out that kissing is its own kind of fitness workout that both burns calories and requires significant muscular coordination. In fact, a total of 34 facial muscles and 112 postural muscles are used during a kiss. How can you not be completely present when you are deep in a kiss? It’s no wonder that ancient lovers believed that a kiss would literally unite their souls because the spirit was said to be carried in one’s breath. Two people fully entwined in each other’s kiss are united in connecting to the exclusion of all else.
"[...]It is no surprise that kissing is good for you. Studies show that increasing the frequency and dare I say the intensity of kissing in your relationship is found to lower your stress levels and increase your satisfaction with both your relationship and your life. [...]
"Someone once said that kisses are like tears, the only real ones are the ones you can’t hold back; so in the pursuit of a better and more perfect study of philemagtology—don’t."