Surprised Walt Harris hasn't been a name that has been circulated. As far as I know, he hasn't coached since being let go at Stanford. He was a solid offensive coordinator under Johnny Majors in the 80's while at Tennessee. He has also coached some pretty talented receivers when he was at Pitt (Larry Fitzgerald and Antonio Bryant).
Also, Shane Montgomery would be another name to throw around as Offensive Coordinator. He was the former coach at Miami (OH) and was recently let go from that position. He is a possible candidate because taking the OC spot at ISU would actually pay him more than what he was making as HC in Oxford. He was the quarterbacks coach/offensive coordinator when Big Ben was there along with the prolific offenses under mobile QB Josh Betts.
Tony Alford at Louisville may get a look. He has been a running backs coach for 13 years and his record speaks for itself. Coached at ISU in two different tenures.
The most exciting pick for me would be Tony Franklin. I don't care that he got canned halfway through his first full year at Auburn. The guy is an offensive genius. Auburn's best option at QB was a Juco transfer that didn't have a clue how to run the offense. He is going to put points up on the board, especially since the talent at ISU is in place (mobile qb-Arnaud, Tiller; WR options-Johnson, Darks, Hamilton, Jones, Carlson, etc.; balanced backfield-Robinson/Williams, Schwartz