Please note that this is intended as a guideline not as gospel and doesn't allow for personal allergies etc that can arise.
Certain woods are often used for making things that are for use with food that are potentially dangerous. Some are obviously not good such as yew and laburnum, both of which have potential dangers inherent in their makeup. As a simple guide, traditionally things for food have always been made from beech or sycamore, both because of their ability to withstand washing etc and because they are known to have no harmful substances in them. There are those who say that most woods are sterile after being cut but personally I would be wary. It may be a myth but there is a story of the Romans coming over here and seeing the druids drinking out of goblets made of yew. Yew was one of the woods that was sacred to them (the druids). The Romans went ahead and made cups etc from yew and found that with prolonged use they were poisoning themselves. The druids apparently only used them for ceremonial use. If you ere to Google 'toxic woods' you would probably frighten yourself off ever using anything of wood again but be sensible. Something that is going to be taking a pounding such as a mortar and pestle or a chopping board will inevitably have something of the wood in the food so stay safe and stick with beech or sycamore. Hazel is also a safe wood but isn't often found in large enough sections to make things like these.
For those who have access to it (North American turners) maple ( of which sycamore is one) is also considered food safe as the tree family apparently has some anti bacterial properties in it.
Other woods that can be used include cherry and birch (birch sap is used to make a drink as well)
The greatest danger from wood being used for food stuffs is however not so much from the wood as the finishes used. Drinking vessels were traditionally finished off by melting beeswax into the cup so that it impregnated the grain. Modern finishes would include melamine or an oil such as liquid petroleum or mineral oil (sounds awful but is sold as a food safe oil) Vegetable oils can be used as well as long as they are not left untouched for a great length of time as they can go rancid.