Don't worry, you weren't sent back to the year 1999. It's still 2010. The original peer-to-peer music sharing service as hit the Android Market. Only now, it's legall. The app is free, but to access the music, you must be a Napster subscriber -- $10 a month. 

Here is the description:

Listen to your choice of over 11 million full-length songs -- anytime, anywhere, all for just $10 a month. Also enjoy Napster on any connected computer, compatible TV, Blu-ray player, or other home audio products. Sign in today, or sign up for a FREE TRIAL and save 20% with the annual plan. Enjoy Napster everywhere.

Download link after the break.