Current authentication libraries reccomendation

[eluser]msteudel[/eluser]
I know this question get's brought up regularly, but I couldn't find one that was very recent. (Bunch of old ones on Stack Overflow too). I was just wondering what are considered the top authentication libraries that are still active and will/are 2.0 compatible?

[eluser]InsiteFX[/eluser]
Ion Auth in the WIKI

Ion Auth

InsiteFX