From what I gather, the last day is Monday, March 31. No flights thereafter. The news articles are saying to contact your travel agent or credit card companies for refunds.
All of this comes about 10 days after Aloha filed for bankruptcy. There was an attempt to find other buyers, but even with the State of Hawaii putting up a loan guarantee, no luck.
UPDATE (3/30/08 8:52 PM)
Gov. Lingle has asked the bankruptcy court to delay service shut down. Story here.