The regular algebra of a quiver
  Let $K$ be a fixed field. We attach to each column-finite quiver $E$ a von Neumann regular $K$-algebra $Q(E)$ in a functorial way. The algebra $Q(E)$ is a universal localization of the usual path algebra $P(E)$ associated with $E$. The monoid of isomorphism classes of finitely generated projective right $Q(E)$-modules is explicitly computed. 
Pere Ara, Miquel Brustenga