In light of Oakland's victory over Oral Roberts and the AP's false claim that "no Mid-Continent team has been an at-large selection to the NCAA Tournament" (and ESPN's constant reiterations thereof) the following is a (non-comprehensive) list of conferences never to have received an at-large selection to the NCAA Tournament (at least since 1985)...
America East Conference
America West Conference (1994-1996; no automatic bid)
Big Sky Conference
Big South Conference
East Coast Conference (1974-1992, 1993-1994)
Gulf Star Conference (1984-1987; no automatic bid)
Mid-Eastern Athletic Conference
Southwestern Athletic Conference
Without having actually conducted timely research, the following conferences have only one instance of having sent an at-large team to the NCAA Tournament (at least since 1985)...
American South Conference (1991)
Atlantic Sun Conference (1994)
Colonial Athletic Association (1986)
Metro Atlantic Athletic Conference (1995)
Ohio Valley Conference (1987)
P.S. Some numbnuts just sent Dan Patrick an e-mail stating that the 1985 Villanova team only got in to the NCAAs by virtue of winning the BIG EAST Conference Tournament (won by Georgetown); the 1985 BIG EAST sent six (Boston College, Georgetown, Pittsburgh, Saint John's, Syracuse, Villanova) of nine (Connecticut, Providence, Seton Hall) teams to the NCAAs, with four of those teams (BC) advancing to the Sweet 16 and three (Georgetown, Saint John's, Villanova) advancing to the Final Four...(granted, he also stated that North Carolina State might not have advanced to the 1983 NCAA Tournament had it not won the ACC Conference Tournament)...
The Mid-Continent Conference sent an at-large selection to the NCAA Tournament in both 1990 and 1991; conversely, Oral Roberts received an at-large berth to the NCAA Tournament in 1974...