The Dolphins four preseason opponents have been announced. They are the same as last season.
Game 1: home vs Tampa Bay
Game 2: road vs Jacksonville
Game 3: home vs Kansas City
Game 4: road vs New Orleans
No dates or times have been set yet.
As for the regular season schedule, it was supposed to be today. I remember checking out the NFL Network television schedule and seeing the schedule release show listed for today. But that has since been changed. You'll remember that last year, the schedule was supposed to be released during the first week of April but was pushed back 5 days. So the earliest we'll have the regular season schedule is likely next week.
Update [2008-4-3 16:10:17 by Matty I]: The official site does have the dates and times of the home games. Here's how it looks:
Saturday, August 9 - vs Tampa Bay (7:30)
Saturday, August 23 - vs Kansas City (7:30)