My own personal experience has come through the Daito Ryu and Roppokai School through Taiki Okajima, the nominated successor of our Aikido Yuishinkai school.  A lot of material on the Roppokai school is on the web.  Also well known on the aikiweb are IS practitioners Dan Harden (who cites some experience in the Daito Ryu - not sure which school) and Howard Popkin.