Personally, I do not mix different woods in the same room. I just purchased a bedroom set finished in light cherry for the oriental flavor. Walnut is my favorite wood although pretty costly. Being a woodworker and remodeler, I see a lot of mixes from time to time and typically feel that any mix is a mistake. That being said, I have seen different woods that are stained alike that were acceptable to most.
Is this a woodworking question, or a decorating question?
If it's a decorating question, then I agree with Donny in that different pieces of furniture made from different woods will clash.
But if it's a woodworking question, then I'm all for livening up a project with contrasting woods and different colors of stain. Of course, it depends on the project, but contrasting woods, used tastefully and judiciously, can make a piece very striking.
I disagree. I think contrasting woods can be a great compliment. Our kitchen table is birch on top with walnut legs. Then the chairs are all walnut except the seat pad which is a blonde type fabric, which not so coincedentally is pretty much the same color as the birch top. This all sits on our oak laminate floor. All the trim in our house is a medium oak, yet our living room furniture (cofee table, end tables, etc) is a medium cherry, except the entertainment center which matches the woodwork, and our bedroom furniture is dark cherry. It all looks fine.
Sorry for the confusion. Definitely a decorating question. If you look at Will's apartment set on Will&Grace, you'll notice that they mix and match woods everywhere and it seems to work. I guess there's no clear answer to this. =)
Charles, I know what you mean, and thanks for expanding my thinking. I was thinking only of furniture, but if you include the floor, walls, and trim, along with the furniture, then contrast can definitely be good. I failed to consider this possibility even though my own Home Theater (my biggest DIY project, no less) has pickled ash walls, red oak trim, deep red-stained hardwood floor, and a black granite fireplace. It's definitely the prettiest room in the house, if not the entire neighborhood. In a room like that, almost any furniture would look good.
But would I put a knotty pine bookcase next to a walnut rocking chair in that room? Probably not. I think I'd want the unupholstered furniture to have a similar look to it. But that's just me.
Bottom line - it's a matter of taste. Do what looks good to you!