Shamrock Airport Express: (970) 482-0505
Reservations are recommended by 7pm the night before to be guaranteed a seat.  Pickup at DIA is Level 5, Door 504, Island 4.
One-way: $21
Round trip: $42

Rental Car: Make reservations directly with rental company for pickup/return at Denver International Airport.  The E-470 toll road is now completed from DIA to I-25.  There is no fee for parking at the University Park Holiday Inn.