There are many excellent sources of information regarding Argentine Tango on the Web. Below are some links. In summary (a brief and only tangential summary), Tango Argentino has evolved over the past 120 years or so from early Afro-Argentine origins, influenced by the melting pot of broader Argentine society as well as contacts with the European continent.
It remains a street dance; that is, unlike Ballroom Tango, there is no set syllabus determined by a group of professionals. Like a language, people in Boston have different "accents" to their Tango than those in Helsinki, who have different accents from those in Buenos Aires. In other words, while they all can communicate with each other through the dance, all have slightly different ways of doing so. It is easier than some dances in that one may simply walk or stand nearly still while still being considered to be dancing. It is harder than some in that the lead and follow is very dynamic and more subtle and varied.
Greg (med student at the RAHC) started teaching Argentine Tango basics over at the Narciso Martinez Cultural Art center in March of 2005, thanks to the good graces of la directora Cristina Balli. Lori Reed of the RGV Arts Studio has been good enough to host the lessons since around May of 2005, and is due many thanks for her excellent dance space and support.
With Greg leaving for points upriver, some members of the group will continue the weekly meetings on Sunday as both lessons and practice time. Partners will continue to not be necessary.
Rick, coming from LA to teach Physics at UTB, has founded a Tango group at UT Brownsville, and information regarding that is available by phone.
And, if the group continues to grow, touring Argentines may be added to the mix; so please do come and visit and learn and dance!