The theft of the OP could be considered victimless… for now. ::Cues eerie music::
Not being a lawyer, and therefore hoping I am not misunderstanding the term “commonlaw”, I will nevertheless take a stab at this:
How about bigamy, prostitution, or drug use?
All could have victims under certain circumstances, but all could also occur with no obvious victim and yet still be considered a crime.
My all-time favorite (I posted a GQ about why it is forbidden some time ago): Incest.
IANAL, but aren’t all “crimes” codified or on statute books, and therefore not part of common law, which is unwritten?
The laws against bigamy, drug use, incest, etc are written in great detail and have been passed by legislatures, so are not part of common law.
That’s my understanding. (But I certainly stand to be corrected - not my subject at all.)
There is such thing as common law crimes, and there are common law definitions of most crimes, including murder, assault, mayhem, etc. But most jurisdictions have codified the criminal law in statute, partly because of the notion that members of the public should have adequate notice of what actions might be the subject of criminal prosecution. And often the statutory definition of a crime is quite different from the common law definition. Also statutes can categorize crimes differently than the common law. I would think you would find it difficult to find a reference (in the manner of the Restatements of common law) that would detail common law crimes.
I would doubt very much that drug use would have been a crime under the common law.
I wouldn’t be surprised if blasphemy, sodomy, sedition and other religious, sexual, and political acts were crimes under the common law.
acsenray pretty well summarized the answer to your question, Hemlock, but in point of fact there were numerous crimes, including several we would consider victimless (e.g., sodomy and blasphemy, and I think fornication) under the common law. Until some point in the 20th Century (somebody who knows U.K. law can pinpoint when), all these were quite punishable.
In the U.K. and in most U.S. states (and I believe the same holds for Canada, Australia, and Ennzedd), there has been a move to put all penal law in statute and to remove the criminal common law from operation. I’m unsure whether any states can still convict of common law crimes (any U.S. lawyers who happen to know?).
I understand that Maryland was one of the last U.S. states to have criminal common law. I don’t know when they did away with it, though.
“How about bigamy …?”
Bigamy is a victimless crime?! 
If consenting adults chose to form a so-called “plural marriage” and there was no welfare fraud or child neglect involved, who would be the victim?
I think John’s point is that there can definitely be a “victim” in a case of bigamy. The particular set of circumstances you describe is probably “victim-less,” but there a myriad of other possibilities that are not as harmonious (and, in fact probably comprise the majority of bigamy charges in Western nations).
Just wanted to clear this bit up. The common law is not unwritten. In fact, it’s written all over the place. The common law developed through judicial interpretations and appeals to precedent with some generalised legal principles and occasional early English “statutes” thrown in.
This differs from statutory law in that statutes are created by legislatures in a relatively comprehensive and finalised form. They do not evolve from the pontificating of judges ruling on particular cases.
My understanding of John’s point is that there are victims even in monogamic marriages. You’re just going to have twice the trouble if you’re in bigamy.
I agree with Schnitte about two wives being a problem, the poor man has two mother in laws to deal with, that makes him a victim in my book.
AAAAAAH! Spooky, something ate my post.
Maybe I’m misreading this but here are my opines:
Jaywalking.
violation of any self abuse/puritanical laws. (Onanism laws still exist in some places)
posession of proscribed materials. (not USE, but posession. I know some states have some bizarre pornograbhy laws)
Speeding.
Pretty much any and all traffic violations actually (speeding is a seperate infraction from hitting someone. Combine the two and you can get a third type of infraction, same for ignoring yield signs or stop signs.).