The order and duration of each animation is defined in a very simple notecard inside the HUD. This lets you create sequences very easily by editing a notecard such as this :
In this example, the "BellyDance 1" animation will play for 20 seconds, then "boxing" will play for 30 seconds, then "Russian Dance" for 10.3 seconds. After that, looping occurs and the HUD will play BellyDance again.// comments begin with 2 slashes, they are ignored // use comments to enhance readability if needed BellyDance 1:20 boxing:30 Russian Dance:10.3
The only requirement is that the animations are placed inside the HUD's inventory along with the notecard (you cannot specify an animation by its UUID, unfortunately - SL limitation).
The ChainDance HUD automatically detects changes in inventory and reloads the configuration as required. To activate the sequence, just touch the HUD (and watch it spin!).
This applies only to the wearer of the HUD. If you need a device to animate several avatars, then you can have a look at the OAnim HUD !
The ChainDance HUD is completely free and available at Oggy's Scripted Items marketplace and in-world stores. Check it out!