As new sliders debut from Samsung on Sprint and HTC on T-Mobile, Verizon’s Droid 2 is already free with a plan.

Competition is pushing prices down on Verizon’s VZ Android phones.  The newly released Fascinate immediately went free on online discounters like Amazon AMZN and Wirefly.  But that phone is crippled with Bing so its appeal is limited.  Today, Amazon is advertising the Droid 2 for free with plan.  That’s a significant milestone.

The move could also be a signal that a newer version of the phone may be coming out, the Droid 2 world phone, which will work with SIM cards internationally on GSM networks.  Also, there is significant interest in the upcoming Droid Pro, which has a BlackBerry-esque keyboard and works internationally as well.

Microsoft also announced that an LG phone with a slide-out keyboard running Windows Phone 7 will be released with AT&T just in time for the holidays.

And of course there is the competition from Sprint S with the Epic 4G ($149) and T-Mobile with the G2 ($99) which are both solid slider Android phones with physical keyboards. (compared below)

(From the G2 Review)