A stable source for the continuous production of high concentrations of gaseous nitrous acid (HONO) up to 5000 ppm has been developed, characterized, and employed for a study of the near-UV photodissociation of HONO and HONO-water clusters in a continuous supersonic free-jet expansion. The source consists of a flow reactor fed with aqueous reagent solutions purged by an inert carrier gas at flow rates up to 1 L/min. The dynamics of the photodissociation of jet-cooled HONO and HONO-water clusters at 355 nm have been studied by measuring the rotational distribution of the nascent NO (upsilon''=2) photofragment using the laser-induced fluorescence (LIF) technique. Distinctly bimodal rotational distributions have been observed for the nascent, vibrationally excited NO, which are well described by the sum of two components: a Gaussian distribution at high J and a 170 K Boltzmann distribution in the low-J range reflecting photodissociation of bare HONO, HONO-H2O complexes, and small HONO water clusters.