Random Map Generation question

Not quite sure this belongs in the AI forums, but what the heck. I''ve been slightly working on this for some time now, and I have yet to figure it out: how do you randomly generate working mazes? Nothing tricky or anything, just filling up a 20 by 20 character array with either ''.''s or ''#''s, representing paths and walls, respectively. I''m looking for more of an explanation than the code itself, though the code would be much appreciated. And on a completely unrelated note, what would you recommend for easy, entry-level 2D graphics? Nothing fancy, just wanting to make a graphical representation of said maze outside of printing all the individual characters in a console window. Thanks in advance! --------- Krunk