Well in the show they havn't got far enough to tell you but in the book the two As are Mona Vanderwaal and the real Alison.
Hope this helps and hope i didn't give anything away.:)
{SPOILER ALERT: Don't say i didn't warn you}
In the television series, we find out in the season finale that Mona Vanderwaal is "A" but we also find out that there is more than 1 "A". We only know who one of the "A"'s are but hopefully in Season 3 (scheduled to come out in 2012/2013) we will find out who else is in the A-Team.
[SPOILER ALERT UPDATE]
It is revealed in episode 12 of season 3 that the second A is Toby
Yes, Chris Brown will be on Pretty Little Liars. He will be in season two of the show.
Ezra and Aria are in a relationship together on the show Pretty Little Liars. When Ezra accepts a teaching position at Hollis College the two want to make their relationship public but they think it is difficult.
Yes. There is Mona and Alison
Yes there will be a a second season.
no
-A will be revealed on March 19th 2012 But their will be a total cliffhanger and Pretty Little Liars will end somewhere in 2013.
Darren Wilden and Garrett
It may end differently, but only slightly, but there are two As: Mona as the first, and Allison's twin sister is the second.
June 1, 2012 midnight
June 5th, 2012
G6
Two can keep a secret, if one of them is dead.