Great news! Thom Holbrook has updated his site!
His celebration of "Crossovers & Spinoffs" (you'll find the link up near the top of the list to the left) is one of the best online. It really goes deep into the method to the madness of linking certain shows together.
But it had not been updated since back in August of last year, and I was afraid he might have lost the interest needed in keeping track of this ever-expanding concept in Television. However, near the end of last month he posted some new additions to the site, and it's a pretty good collection to mark his return:
Article Added 01/26/06 --> The Fresh Prince Of Bel Air crosses over with Blossom.
Article Added 01/26/06 --> Beavis And Butt-head cross over with The Head.
Article Added 01/26/06 --> The Drew Carey show crosses over with Norm/The Norm Show.
Article Added 01/26/06 --> Gilligan's Island evloves into The Real Gilligan's Island
Article Added 01/26/06 --> Strange Luck name drops The X-Files
Article Added 01/26/06 --> The Surreal Life spawns some Strange Love
Here's hoping it's just the beginning of regular updates!
I just looked in at Crossovers & Spinoffs, and Thom has added even more crossovery goodness in the last two days. Check it out; he has a fun way of looking at this venerable building block for the TV Universe!