Town have transfer listed Gavin Williams, Billy Clarke, Dan Harding, Matt Richards and Gary Roberts. All five are in contract, but rarely featured during the second half of the season.
Boss Jim Magilton told the club site: "We will listen to enquiries for the five players. If we don't get any interest that suits all parties then they will obviously be welcomed back for pre-season.
"I think it's important that these guys play regular football and, if it works out that they have to move on to get that, then we won't stand in their way."
Richards spent much of the season on loan at Brighton, who may be keen to sign him permanently, while Clarke spent the final part of the season with Falkirk. Roberts had a spell with Crewe Alexandra.
Williams, Richards, Harding and Clarke are all out of contract at the end of 2008/09, while Roberts has a further year on his Portman Road deal.