I set up a bowl full of marbles to provide water for my bees last year. It’s very pretty and it works, but I’ve recently switched to using a chicken waterer instead:The bowl full of marbles isn’t difficult to maintain, but the I prefer the chicken waterer because, for me, it’s more practical.
Postscript (10 days later): Now that we’re at Newfoundland’s height of summer (I guess), the bees are on the chicken waterer all the time and seem to suck down about a litre of water every two days. At any rate, that’s how often I refill the Mason jar. A larger bucket-sized chicken waterer would probably work too.
See Watering Bees for an overview of several watering methods.