I used to deal with mercury spillages frequently at work.
The longterm danger is from the mercury vapor.
Normal proceedure is to carefully, gently sweep up, or suck up with a dropping pipette or syringe, as much of the droplets as you can. Any you collect should be put in a jar with a little water in it to await disposal - the mercury sinks below the water so that there is no longer exposure to the vapor.
As mentioed above, dusting with a mixure of sulphur and calcium hydroxide, or using them made into a paste is the next step - I use the powders as it can be brushed around the area of spillage. This can then be swept up and bagged for normal refuse.
Twice in the last few years, we have had parts of Ely sealled off and the fire brigade out in full chemical suits because of mercury spills - once at a jeweller's shop and once at the auction house when a barometer was broken. At the time, when asked for advise at the school I work at, I almost managed to convince our Operations Director that the first signs of mercury poisoning were that you grew taller in hot weather...
