Whew - another encyclopaedic question  
 
 
Right - all yeasts you'll commonly come across used in bread-making, brewing, mead-making, wine-making, anything to do with alcohol-making are the same - Saccharomyces ellipsoidius (hope I've got my spelling right). What's happened over the years is that certain strains (but same species) have been developed for certain jobs. All of them will produce alcohol and carbon dioxide, but not all of them are as good as others at specific jobs. So, Bakers' Yeast produces more CO2 than alcohol - great for bread-making. But you can still get it to produce a 10% ABV drink if you're nice to it. Brewers' Yeast is geared more to the alcohol production and, I'm informed, to specific flavours in the finished product. You could still make bread with it, though, although it may take a little longer. There are lots of Brewers' Yeast varieties. WIne yeasts - you already know what I'm going to say, don't you? - are geared towards wine production. Under normal conditions, Wine Yeasts will tend to produce a bit more alcohol than Brewers' Yeasts (but who wants a 12% ABV beer?), which tend to produce a bit more alcohol than Bakers' Yeasts.
But that all depends upon how much sugar you give 'em. They all stop producing anything if their food runs out - and that's sugar. So, if you were making an elderflower champagne, for instance (low in alcohol, so low in added sugar), you could get away with a Bakers' or Brewers' Yeast. If you want to make a super-duper strength elderberry wine at, say 17.5%, you need a good Wine Yeast, preferably developed specifically for heavy red wines (and you need to treat it like a baby).
A lot of recipes call for a Champagne yeast when it's simply not needed - it's just a bit of wine snobbery. Champagne yeast is one which is very tolerant of alcohol (which, ironically, is toxic to yeast) and tends to be used to extract the last tiny bit of sugar from a must (best Champagne's are dry, you see). That characteristic also means that it may be able to restart a "stuck" fermentation, which is the ONLY reason I would consider using it.
For 99% of all known household germs, general-purpose wine yeast will do the trick (if you're making wine, of course). Most of the rest is hype. Dunc's the man to ask about Brewer's Yeast and I'm sure he uses a few special ones. But I'd bet he says much the same thing - if you just want a pleasant beer, use the stuff everyone else is using.
Mike