Well, I have a whole run of those sounds. Here's how a typical round goes for our tournaments:
"Twenty minutes to go"
"Fifteen minutes to go"
"Ten minutes to go"
"Five minutes to go"
"Three minutes to go"
"One minutes to go"
"Thirty seconds to go"
"Ten seconds to go"
"Five seconds"
"Three"
"Two"
"One"
Microsoft sound - TADA (from Windows XP) plays for the end of the round. Players have told me that this sound seems to happy for the raising of the blinds, but we all love it anyway.
For the end of the game, I have Strong Bad saying "It's over!" for normal tournaments, and an hockey air horn (the one you hear when the home team scores) for major tournaments.