During most of my workshops I am using hourglasses.  It works great for facilitated meetings and standups. The different colour hourglasses, all have a different time. F ex the purple one is great for standups as it’s 15 minutes.
Next to that, they also works great to have them in a meeting room.
The rules for a meeting are: anyone that thinks that a discussion in the meeting is taking too long, can select one of the hourglasses and turn it around and tell his co-meeter: let’s discuss this only for this amount of time.

I have hourglasses of

• 30 minutes (black)
• 15 minutes (purple)
• 5 minutes (blue)
• 3 minutes (yellow)
• 1 minute (green)
• 30 seconds (orange)

When the hourglass runs our, the people in the meeting vote together if they want to keep on discussing or go on.

• Thumbs up ==> go on
• Flat hand ==> I join the majority
• Thumbs down ==> let’s move on

Last Monday during another successful GTD/personal kanban course, I got again the question about where I bought them.

These days I buy them at Team Building Shop
You can also buy them from amazon. I use amazon.co.uk

Update: these days I prefer using a timetimer, as that works for anytime