Cammack, who netted 110 times in 245 appearances in claret and blue, was back at Glanford Park to speak to fans prior to the 1-1 draw with Brentford.
"Anything the supporters trust can do can only be a benefit to the football club," said Cammack.
He follows in the footsteps of fellow fan favourites Cliff Byrne and Alex Calvo-Garcia in joining the Trust.
The Iron Trust was launched in the summer with the aim of giving supporters a greater say in the way the club is run.
It now has almost 150 members. The Trust recently completed its first purchase of £100 of shares in the club, and has looking to build that to £1,000 in the coming months.
It has also agreed to hold regular meetings with the football club's board of directors.
Membership of the Trust until the end of the 2012/13 season costs £10 for adults, £20 for families (2x adults and unlimited U16s) and £3 for U16s. You can join online at www.theirontrust.com