Gay's agent, Albert Elias, told The Associated Press that the deal is worth up to $17.6 million. Gay was an unrestricted free agent.
"Randall is a player we targeted early on in this free-agent market, and we're extremely pleased to have him on board," said Saints general manager Mickey Loomis.
Signed out of LSU in 2004 by the Patriots, Gay has recorded 83 career tackles and five interceptions and recovered three fumbles, including two returned for touchdowns. He played in all 19 games for New England in 2007 after his previous two seasons were cut short by ankle and hamstring injuries.
Running back Aaron Stecker, who rushed for a career-high 448 yards last season, also agreed to re-sign with the Saints according to The Associated Press.
Terms were not released. Stecker had been an unrestricted free agent.
"We made re-signing Aaron a priority because it takes continuity to build on what we've been able to accomplish on offense the last two seasons," Loomis said.
Stecker, who originally signed with the Saints in 2004 after four years with Tampa Bay, scored five touchdowns and caught 36 passes in six starts last season.
McCray, 26, will sign a five-year, $20 million contract, according to ESPN.com's Len Pasquarelli.
Despite slumping to only three sacks in 2007 after a breakout season the year before, the former University of Florida standout is regarded as a strong outside pass-rusher. McCray likely will become the Saints' No. 3 end behind the starting tandem of Will Smith and Charles Grant.
McCray's best season was in 2006, when a season-ending Achilles injury to Reggie Hayward forced him into the lineup and he registered 10 sacks in 12 starts.
A seventh-round pick in the 2004 draft, McCray has 94 tackles, 22 sacks, seven forced fumbles, three recoveries and five passes defensed. He has played in 61 games and started 29 of them.
"Bobby is a player we identified as being able to come in and help us in the defensive line rotation," Loomis said.
-- ESPN.com's Len Pasquarelli and The Associated Press
Bentley was considered a valuable role player on the free-agent market because he is an exceptional special-teams player along with having the ability to fill in as a starter when necessary.
He was drafted in the fourth round of the 2002 draft by the Cleveland Browns. He spent three seasons with the Seahawks and started five games in that span.
-- John Clayton, ESPN.com
Hartsock, who was drafted in the third round in 2004 by Indianapolis, is best known for his blocking ability. He has just 24 catches for 247 yards in 45 career games, including 12 catches for 138 yards with Tennessee last season.
Hartsock's deal is for four years and $9 million.
-- ESPN.com's John Clayton and The Associated Press
Included in the deal is $3 million in guarantees. Gaines started his career as a blocking tight end in Carolina and ended up going to Buffalo, where he developed some of his receiving skills last season.
The Lions hope he can be a 40-catch tight end, but they are counting on him to improve their run blocking.
-- John Clayton, ESPN.com