Hokkadio Access Network has a network of buses between Sapporo city & airport to Niseko. I booked a bus + lift ticket package for 5500 yen which included an 8 hour lift ticket for Niseko Village, and bus trip one-way from Chitose Airport to Niseko, and return one-way Niseko to Sapporo.
They have other routes and combinations which can be found here.
Normal price for the bus one way from Sapporo or Chitose Airport to Niseko is 2300 yen or 4600 roundtrip. For only 900 yen more, I was able to get a lift ticket for one area of Niseko United (4000 yen if purchased separately.)
I called, but you can also e-mail the company since their speaking English isn’t too good. Upon arrival at Chitose airport I walked over the counter #5 in the domestic terminal and paid cash for the package and was told which bus I’d be on and where the line-up was. They don’t speak much English but you can pretty much gather what’s going on by following all of the Japanese people and the signage. I was given a voucher for the lift ticket redemption, but there are no bus tickets, they just use your name. Make sure you check-in, they didn’t have my name on the list and had to re-confirm with the desk.
The bus was door to door from the airport to the Hilton Niseko where I was staying. On the return it was also door to door from the Hilton to my hotel in Sapporo, the New Otani Inn. There was an agent waiting in the Hilton lobby already when I got downstairs so I checked in and she notified me when the bus arrived, all fairly easy.
The lift ticket redemption was also very easy, like the Yokubari Pack, you just go to any lift ticket window and present the voucher. They’ll give you a lift ticket after you give them 1000 yen for a refundable deposit.
I highly reccommend making reservations ahead of time, as if you go on a busy day they may not have any seats, you don’t need to pay in advance anyway so it really doesn’t hurt. This is a great deal to get a lift ticket for cheap. Other companies may have similar packages, but I didn’t see many from the airport, most of the lift ticket packages were only from Sapporo city.