"100 Years" by Five For Fighting might be an appropriate song for a funeral. The song is a retrospective on a person's life, and it's very soft and pretty.
I've always thought that a great funeral song would be "Dust In The Wind" by the rock band Kansas. The instrumentation is solemn yet accessible and the lyrics are pertinent and coupled well with the singer's voice.
Funeral is a sad occassion and hence bhajan type of songs or instrumental music are suitable for playing during funeral. Some instrumental music like shehnayi vaadan also is suitable during funeral.