On Wednesday's season finale of Bones, Billy Gibbons from ZZ Top was (obviously) reprising his role as Angela's dad. Also, the mom of the victim was Roxanne Hart, who I remember many moons ago as the love interest in the first Highlander movie.
24's Karen Hayes (Jayne Atkinson) was the FBI boss on the season finale of Criminal Minds.
I mentioned it previously in my Lost post, but Tracy Middendorf was one of the mysterious inhabitants of the Looking Glass.
Dayton Callie (Charlie Utter from the dear, departed Deadwood) reprised his role as Miniature Killer (foster) dad Ernie Dell on Thursday's CSI: Original Recipe finale. The MK's "real" dad, a fucked up Vegas ventriloquist, was played by Jay Johnson. Sitcom savants know Johnson as "both" Chuck and Bob from the seminal sitcom SOAP.
Sorkin good luck charm Josh Malina unexpectedly showed up on Friday's fun Stargate SG-1 as the only one of the "hostages" to believe in aliens.