Comic Con is the biggest event of its kind in the world. This year's geek-fest will take place in San Diego from July 22 - 25. Most TV panels will take place on Saturday (24 July) and Sunday (25 July). For shows such as Supernatural, Smallville Chuck, The Big Bang Theory etc, check out the schedule at TVOvermind.
TV Guide has teamed up with Warner Brothers to released special edition with four different covers including Smallville and The Big Bang Theory. Details here. Fans can pick up the mags from Comic-Con exclusively at the Warner Bros. booth, #4545. The special issue will also be on newsstands on Monday July 26. I think Fringe will get the 3rd cover, not sure about the 4th one. But it'd be awesome to see a Supernatural cover!