Steve - Graham mentions toxicity of some woods. I'd go a step further and say treat all woods as toxic so use a good dust mask at all times and an extractor when sanding. Once dust gets into your lungs it's there for good.
When I started I was told to use the cheapest wood that I could find and that bog standard pine from a diy shop was good to practice on - if you find a cheap enough source you won't worry about wasting it and can spend time turning it down to nothing. It can be difficult to get a good finish on it from the tool, but if you can manage it on pine it should stand you in good stead when you move to hardwoods. This pine is probably only suitable for spindle turning though.
The couple of times I've been to Snainton they've had plastic sacks of random wood that have been pretty cheap. The one I bought had plenty in it. Last year at the Harrogate they had some good bargains on some of their blanks.
One source of free wood I found recently is the council depot close to where I live. They use it as a storage/composting place for all the trees and bushes that get trimmed or chopped down in the city parks and streets.
The problem with using free found or given wood to learn with is that you will have to convert it into a usable blank for mounting on the lathe. For this you will probably need a chainsaw and/or a bandsaw.
You're also likely to encounter less than ideal wood with faults in it that an experienced turner may use to his advantage but may prove difficult or even dangerous for a beginner to deal with.
Even if you manage to turn something to your satisfaction if the wood was wet when you turned it you may have to consider part turning to finish later, turning thin to allow movement or drying using a microwave.
I would suggest that whilst learning it's easier to buy ready dried and prepared wood. Maybe it's just because that's how I learned.
And as Andrew says - try to get to Harrogate next month even if it is just to see some of the demos from some very well known UK turners.
Ah - I've just re-read your question and it wasn't really about where to get wood from, but suitability for use.
For an item in contact with food you want something resilient, non-toxic and non-tainting - this has traditionally been beach or maybe sycamore (if you have a look at wooden spatulas or spoons they're usually beach).
If you're making something decorative it can be pretty much any wood. If the decorative piece is to show off a certain form or is to be embellished (eg with carving) then you may want something with bland grain or colouring or which holds fine carved detail well.
If you're making a pen then generally go for something with a strong grain or colouring.
I find Mark Bakers book
Wood for Woodturners an interesting read. It lists common woods, how well they turn, what the wood qualities are, how well they finish.
(sorry,Graham,couldn't resist it :wink: )
