At the moment, I can think of two things where the left and right disagree on, but should co-operate on:
Evolution and free-markets
Huh? What's the similarity here? Equilibrium is the name of the game. Typically, the left are "open-minded" individuals who can come to believe in this bottom-up theory of evolution. They will accept it as a mechanism that could have brought about life without the need for a top-down creator. On the other hand, we have the religious conservatives, who seem to always side with the right-wing parties (Republicans, Liberal Party of Australia, etc.) who believe in the bottom-up workings of a free market to achieve better results than a top-down centrally planned system.
So to liberals (evolution believers): you know that bottom-up evolution stuff you believe in? Well, free markets are just like that, so ahh chill out dude.
To conservatives (free market believers): you know that bottom-up system of free enterprise you believe in? Well, evolution is just like that, so yeah..
Unions and CEOs
Unions: the left view them as a beacon of justice and fairness, the right view them as the scourge of inefficiency.
CEOs: the right view them as masterminds of efficiency, and the left view them as hoarding excessive wealth at the expense of the worker.
They're both just self-interested groups though. The fault does not lie with unions or the CEOs, it lies with the government that succumbs to the pleas of special interests. Unions who wish to further the protection of workers should seek to do it through their own means, rather than by an extension of power by the government. Similarly, CEOs who plea for tariffs and regulation against other competitors should not be granted it. Both are necessary and fully justified, as long as they act as fully voluntary and non-coercive entities.