Reddit's college football stream put up a list of college football teams who have reached the top of the AP poll, and the list only contains 44 names. quick look brings up a few interesting points of data.
Mississippi State is the newcomer to the list and is the 44th school to attain #1 in the AP poll.
Cornell is the one school to make #1 that is no longer playing D-1 football and while they were #1 they were involved in the original "5th down" play in college football.
Cornell reached the top spot in 1940 and was riding an 18-game winning streak when they played at Dartmouth. The game was scoreless into the 4th quarter when Dartmouth kicked a field goal to take a 3-0 lead. Then with less than a minute to go, Cornell was at the Dartmouth 6-yard line with a first down. Three plays moved the ball to the 1.
With seconds remaining, Cornell threw an incomplete pass into the end zone on 4th down. One official signaled first down for Dartmouth at their 20-yard line. The head official disagreed and put the ball back on the 6-yard line giving Cornell an extra down, where they threw a touchdown pass with less than 5 seconds remaining to win 7-3.
Later when the mistake was discovered after reviewing game films, the Cornell team and Athletics Director sent a telegram to Dartmouth offering to forfeit the game. Dartmouth accepted, and it is in the record books as a 3-0 Dartmouth win.
Funny, I don't remember Colorado sending a telegram to Missouri after they were given a 5th down at Missouri in 1990 that enabled the Buffalos to beat the Tigers 33-31. That BTW, is the last time that Colorado attained #1 status in the AP poll.
The team currently playing D-1 football with the longest dry spell? TCU, which reached #1 in 1938. The Horned Frogs went 11-0 and won the National Championship behind Heisman Trophy winner Davey O'Brien. TCU opened the season with a 13-0 win over Centenary and closed with a 15-7 win in the Sugar Bowl over Carnegie Tech.
Texas last reached #1 in 2008.
Texas A&M was #1 under Bear Bryant for a while in 1957. That means the Aggies are 36th out of the 44 teams in terms of length of time since attaining the top spot. Teams that have been #1 since A&M include:
Army - 1958
Minnesota - 1960
Northwestern - 1962
Purdue - 1968
Clemson - 1981
Pittsburgh - 1982
Iowas - 1985
Virginia - 1990