Seven of Nine returned to the Alpha Quadrant with Voyager and her crew. In the novels she broke up with Chakotay and joined a think tank- (non-canon) but to know for certain go to []
She joined the Daystrom Institute (where a few famous others, like Geordi La Forge, worked). She did this after she resigned from Starfleet in protest of them cutting off their Borg defence program.
http://www.startrekonline.com/node/201/long : See this for details