Well, syncopation is a general term for “a disturbance or interruption of the regular flow of rhythm”: a "placement of rhythmic stresses or accents where they wouldn’t normally occur. (form da Wiki) It’s easier to understand if you hear it. Try listening to The Entertainer or *The Maple Leaf Rag *or The Syncopated Clock (or even Ragtime Cowboy Joe) on YouTube and you’ll probably get the idea.
Any examples from Robert Johnson?
Well, http://www.robertjohnsonbluesfoundation.org/, has some of his music available (it’s in the upper-right). I’m not where I can check and see what they offer, but it’s Johnson, it’s all good. Oh, and the Internet Archives, at http://archive.org/details/RobertJohnsonMp3AudioSongs has a bunch more, but I don’t see anything I’d recognize as ragtime right off.
Wiki says that syncopation is used in Jazz and the Blues. I thought I might recognize something.
Well, syncopation is used in both, but in Jazz more than Blues. There’s quite a bit of overlap. Sugar Blues has quite a bit of syncopation, St. Louis Woman not so much. Try Tiger Rag on Youtube, or Play A Simple Melody.
U2’s *Pride (In The Name Of Love) *is a familiar song with some very obvious syncopation:
The instrumental parts are very straight, 1-2-3-4, almost march-like. But Bono’s vocal line, particularly on the verses, is very syncopated. Listen to the way most of his words land on the “off” beats in between the 1-2-3-4 of the drums.
A “recent” ragtime composition is William Bolcom’s “Graceful Ghost Rag” - very beautiful!
I once attended a lecture of Paul Tanner, a UCLA music professor of jazz. He told us that the makers of The Sting asked him if ragtime music would be a good choice for the soundtrack. He told them no, it was no longer popular in the 1930s and still years away from its resurgence in the 1950s. He laughed that he was happy they ignored his advice.
I couldn’t catch it there, but Mrs. Plant (v.3.0) found some English guy on the web talking about it. He played “Ain’t [Missbehaving](ain’t misbehavin sarah vaughan)” and I have at least a vague idea. 
In the final section of Joplin’s “Fig Leaf Rag” he momentarily takes the piece from Eb major to Gb major. That half of a measure is one of the most beautiful things I’ve ever heard.
nm
Correcting my botched double post.
The magic moment I referred to can be heard here
*Scott Joplin - Fig leaf rag - YouTube
*
at the 3:46 mark. And again at 4:16.
Thanks, TC.
