Relegated Cheltenham Town sign former Oldham Athletic striker Amari Morgan-Smith on a one-year deal.
Grimsby sign Cambridge United forward Nathan Arnold on a one-year deal while midfielder Craig Clay signs a new one-year contract.
Conference club Welling sign former AFC Wimbledon midfielder Ricky Wellard following his exit from Sutton United.
Chief executive Mark Ashton says players are attracted to League Two side Oxford because of the club's "vision" for success.
Newport County manager Terry Butcher makes his first signings since taking over the Exiles recruiting three new players.
Plymouth Argyle's board of directors will meet on Friday to begin the search for a new manager after John Sheridan left the club.
Hartlepool have made their second summer signing with the capture of striker Rhys Oates.
Accrington Stanley have announced the signing of versatile defender Matt Pearson on a one-year deal.