Nobody really knows what his formula is or how often he tweeks it.
Formula's been on ESPN.com for literally years now. Here you go:
HOLLINGER'S FORMULA
RATING = (((SOS-0.5)/0.037)*0.67) + (((SOSL10-0.5)/0.037)*0.33) + 100 + (0.67*(MARG+(((ROAD-HOME)*3.5)/(GAMES))) + (0.33*(MARGL10+(((ROAD10-HOME10)*3.5)/(10)))))
SOS = Season win/loss percentage of team's opponents, expressed as a decimal (e.g., .500)
SOSL10 = Season win/loss percentage of team's last 10 opponents, expressed as a decimal (e.g., .500)
MARG = Team's average scoring margin
MARGL10 = Team's average scoring margin over the last 10 games
HOME = Team's home games
HOMEL10 = Team's home games over the last 10 games
ROAD = Team's road games
ROADL10 = Team's road games over the last 10 games
GAMES = Team's total games
Only thing missing is after 40 games, the "last 10" stuff becomes "last 25% of the schedule".