Married with Children: Not much has changed except for a few. The series debuts on March 15, 1987 instead of April 5 like IOTL. With David Garrison still on It's Your Move, Steve Rhodes is played by Charles Rocket. The series gets a 12th season as FOX doesn't move it to different slots on different nights, and gets a proper finale with the Bundys winning the lottery.
MWC Scenario 2: It still gets cancelled, but FOX decides to pick up the spinoff to MWC entitled NO MA'AM. That runs until 2000.
Beverly Hills, 90210: Premieres in 1989 instead of 1990.
Also, creator Darren Star goes with his original idea (Potomac, 20854. He is from Potomac, MD). The show only lasts one season.
Freaks and Geeks:
Scenario 1: Judd Apatow's friend at FOX, Peter Roth, isn't replaced by Doug Herzog from Comedy Central, and the show Sick In the Head (a show about a young therapist. It would have starred David Krumholtz, Amy Poehler, and Kevin Corrigan) is ordered to series in Jan. 1999. As a result, Apatow and Paul Feig decide to put Freaks and Geeks on the back burner.
Scenario 2: The show lasts two more seasons. We get to see Lindsay, Kim, Ken, Nick, and Daniel (after he dropped out and back in) graduate.
Fates of the cast:
Weirs: Lindsay's parents would find out about her tour with the Greatful Dead. Also, Paul Feig mentioned something about how she may have had to deal with an extended acid trip or soemthing. She is probably grounded for several months, and her 11th grade year turns out to be a waste. However, I can see her buckling down and doing well her senior year, which gets her into a good college. As for Sam, Feig talked about making him a drama club geek. I am not seeing it. I think that Sam wanted to get away from "geeky" pursuits (he probably only played D&D in the season one finale because Daniel played). If I was responsible for writing a second season, I would have had Sam work with his father at the new department store (Harold's store, A-1 Sporting Goods, would have closed down because of the opening of the big box store) to save up for a car and to be able to fund his lifestyle. I would have also had him become cooler slowly but surely (and taller if John Daley got tall around that time) and start dating more (I would have had him going out with Maureen Sampson, and I would have also invented a new character for him to go out with that he also had a crush on [she would be a year younger, and she would have been played by Kaley Cuoco or Mischa Barton]).
Freaks: Since Lindsay's parents found out, I could see them telling Kim's mother about what they did all summer. Also, I think that Feig was thinking about making Kim pregnant (from the Dead tour, not Daniel). Her junior year wouldn't have been much better than Lindsay's. Also, I can see Nick breaking up with Sarah (after telling her that he still liked Lindsay). However, his feelings for Lindsay wane after junior year, and he gets a new girlfriend. He also continues to work with Harold Weir and take drum lessons, and he joins the Army upon graduation (his dad would have made him).
As for Daniel, I can see him dropping out for a time, but after Mr. Rosso talks to Nick and Ken (and maybe Lindsay depending when it happened), Daniel decides to return after finding out that he only needs 10 credits or so to graduate. After saving up from some part time jobs, he eventually goes to an auto tech school. Him and Sam become better friends as the show goes on. He still also plays D&D with Sam (and Bill, Gordon, and Harris) from time to time when they can. Ken even gets involved with it.
Geeks: Feig said that Bill would have eventually become a jock. I am not sure how that would have worked out. I know that Martin Starr was a jock in real life, but his character was pretty uncoordinated and immature. As for Neil, though, I can see him becoming a part of the Glee Club like Feig said that he would have (to separate himself from his parents and their failing marriage). He also starts to grow apart from Bill and Sam.