I set up a playlist and added some songs from iTunes U. The songs show up in iTunes in my playlist, but don't sync to the phone. The iTunes songs themselves sync over, but they don't go over into the playlist. I also checked "add to playlist" in iTunes in iTunes U.
That has nothing to do with the problem and is a bit of a rude RTFM. If you don't understand the problem please don't regurgitate links. It's not only unhelpful it's rude and shows you to be inconsiderate of others as you couldn't be bothered to read and understand the question.
The problem is a purposeful design flaw in iTunes. It does not list playlists for iTunes U material under the playlists heading. Instead it puts them under iTunes U. The problem with that is it doesn't actually use your playlist so you get a seemingly random sorting of the lectures. Again, this is on purpose and is a horrible, horrible anti-Apple, anti-intuitive, anti-common-sense "design." Basically who ever made this decision hates your freedom and probably kittens and rainbows too.
Answer: The way to fix it is to go in and manually edit the files so their type is no longer iTunes U. You can do this by selecting the files you want to have a playlist for, right click (control click), and select Get Info. Now choose the last button at the top of the form that pops up (Options), now change the type from iTunes U to Podcast or Music. You can do this on the files already on your iPod/iPhone or in your library.
Regarding the playlist. The one way that I have found which works is to create the playlist within one's device. The rest of this message is for those who might be having sync problems where video is not transferred.
Short Answer:
What worked for me in recovering sync capability was simply opening Activity Monitor and stopping the iTunesHelper app, which seems to have unlocked the communication problem.
