JPride,
I've had success with A&R's responding (By success, I mean just having them respond was an accomplishment). However, these A&R's are at the label one day, then on the street the next. The turnover rate with A&R's today is crazy. The best approach that I've found is contacting a higher source...either the VP of A&R, VP of Creative, or the VP/Upper management of the label! These are the people with the final say anyways, so why not have them hear your music.
Make sure you only send ONE track, they don't have the time, nor do they want to sit and listen to your tracks all day to find one hot one. Send the best track you got, keep the message short and honest (don't lie about placements or artists you haven't worked with...they'll find out), and provide a link to a site where they can hear more of your tracks if they are interested. Provide all of your contact info. & Last but not least, make sure you copyright all of your music before soliciting all of these labels and execs.
There are plenty of resources out there that will provide you with contact info for the major and inde label contacts. But the a&r directories are outdated daily, so focus on sending to the department "heads" first (urban, pop, rock, creative, etc).
Good luck