Up until now Firefox OS devices have only been available to developers and in limited quantities. But starting tomorrow people in Spain will be able to get the ZTE Open through Telefónica, for just for 69 euros (about $90) or 2.38 euros ($3.10) per month on a two-year contract. This is the first consumer Firefox OS handset to hit the market and will be followed later on by the Alcatel One Touch Fire.

Further details remain scarce until other manufacturers and wireless carriers make their own announcements, but Mozilla says they are working with more than 20 hardware and operator partners around the world. Only 21% of global mobile subscribers have smartphones, according to estimates, and though competition is fierce, the company hopes to capitalize on this with budget devices built entirely on open web technologies.

Telefonica will be taking Firefox OS to Latin America later this year, while a Norwegian carrier called Telenor plans to sell handsets based on Mozilla’s mobile platform in Central and Eastern Europe.

Announced at Mobile World Congress in Barcelona earlier this year, the ZTE One has a 3.5-inch screen paired with a 1GHz processor from Qualcomm and 256MB of RAM. Other specs include a mere 512MB of onboard storage and basic features such as a 3.2-megapixel camera and support for Wi-Fi and A-GPS.

On the software side of things, Mozilla says Firefox OS includes all the things people need from a smartphone out of the box – calls, messaging, email, camera and more. It also includes built-in social features with Facebook and Twitter, Here Maps with offline capabilities and smart walking, driving and public transit directions, Firefox browser (duh!) and “a new ability to discover one-time use and downloadable apps.”

Additional HTML5 based apps can be downloaded through the Firefox Marketplace.

Check out the video below for a quick look at some Firefox OS features.