The club also announced the re-signing of defensive back Coye Francies, who appeared in 15 games for the Raiders a season ago.
The 26-year-old Maiava started 13 games for Cleveland in 2012, notching 53 tackles. A source tells PFT Maiava received a three-year, $6 million deal from Oakland.
Sims, 27, joins the Raiders after five seasons with the Bengals. He has primarily been a reserve the last two seasons.
Hunter, 29, missed the 2012 season with a triceps injury. He was previously with Denver. He has recorded 11 sacks since entering the league in 2006.