Mobile ad network Millennial Media is releasing its monthly mobile mix report today. According to Nielsen, Millennial’s ads reach 63 million of a total of 77 million mobile web users in the U.S., or 81% of the U.S. mobile web. In July, Android OS grew at a faster clip than in June, with requests increasing by 47 percent, compared to a 23 percent growth in the previous month. Since January, Android OS requests have grown 690 percent. Android has also surpassed RIM to became the number two OS on the Millennial network (surpassing RIM).

Apple ad requests increased 24 percent month-over-month, and are up 15 percent since January. However, iPad requests continue to show massive growth, rising 327 percent in July. RIM ad requests increased 18 percent month-over-month, rising 66 percent since January.