In a return to the early days of vaccine development during which effective vaccines were produced against viruses, virus-sized vaccine delivery systems have made a comeback. Using modern production technologies these nanoparticles have proved to be very effective at inducing cellular and humoral immune responses. Here, we review a number of vaccine delivery systems based on nanoparticles in the size range of typical viruses. Different strategies for generating these particles, ranging from recombinant virus-like particles to inert nanobeads via ISCOMs and nanoparticle-based DNA vaccine delivery systems, are discussed. In addition, possible mechanisms of immune induction are explored.