I don't think there is any specific site or list of programs that would take a transfer. You would just need to contact the programs and ask them if they would consider you. We have had transfers, but never have actively looked for them.
And, I would say yes you will have to interview with them.
Many programs have people leave for numerous reasons along the way so many technically have spots available. For example my program would have at least one spot in pgy3, 4 and 5 next year. The program director is not necessarily looking to fill them, but likely would consider it if a good candidate showed up looking.
