These have got to be the easiest tables in the world.  Basically, you find a candle holder that looks like a table base and add something for a tabletop.  You see these in a lot of dioramas online.  Unfortunately, while some look very much like tables, others still just look like a candle holder with a mirror or something stuck on top. So be careful what you go with.  When you're considering one of these in a store, take out the candle and/or the glass part the candle rests in and find something (a coaster or whatever) that looks at least somewhat like a table top and try it on for affect.  Set it on a shelf and take a good long look.  Ask yourself, "If this were human size, would it look good in my living room?"  If in doubt, pass on it.  I've rejected quite a few using this method and found some others I just love.  Anyway, here are some of my table bases:

The table tops I've seen used most often are mirrors. These are cheap and work quite well, especially in a contemporary room. I also use pieces of glass, but mirror has the advantage of being opaque.  You can't see through the mirror as you can with glass, so you can cover the candle hole in the top of some of the holders.  If you are using mirror or glass, see if you can find pieces with beveled edges, as they look more realistic.  You can sometimes find these at dollar stores or places like Big Lots. I found some of my bigger pieces and oval and square pieces at a store that sells glass for people who make stained glass objects as a hobby.  They apparently use some of these beveled pieces in their projects.
You can also use coasters.  These come in a million colors and can look like wood or marble.  Just make sure they aren't too thick.  Decorative lids from boxes work well if the edges aren't too rounded.  Here are a few of mine.

The glass pieces are especially useful.  With a number of these you can use almost anything for a base.  The oval piece is a favorite of mine, because it is the perfect size for a coffee table. 

Figuring out which tops go with which bottoms is fun.  You can play around with them till you find the combination you like best.  I don't attach the tops so I can keep trading them around and so they are easier to store.
  

Yes, this, too, is a candle holder!

Coffee tables are a little harder than side tables.  Actually, you can use a side table for a coffee table, but I prefer oval or oblong tables for some reason.  Below are some I've found.

I don't quite know what this black thing with the mirror on top was originally supposed to be.  I bought it at a Mission Thrift Store. It doesn't really look like a candle holder or anything.  Anyway, I thought it made a great coffee table in the Black and White Room.  Keep in mind that there are lots of things like this, or the one below it, to adapt.

This one is a plain, unfinished plant stand from a dollar store.

These are actually display pieces they use in stores. They are clear plastic and come in various sizes. You can sometimes find them in Best Buy or at office supply stores, or look around at garage sales. Small ones can be used as side tables, larger ones as console tables or desks.

These are the hardest to find, so I have a number of plastic Barbie tables that I use as well as a number of wooden tables.  (My favorite can be seen in the Failed Dining Room.)  The plastic tables can be painted, since they mostly come in pink.  Gloria sets work well, too, but the chairs are sometimes a little under scale.  (For those who have never seen it, Gloria furniture is plastic Barbie sized furniture, usually done it vivid shades of pink.  It is usually rather well done, but looks better if spray painted or hand painted to more realistic colors.  Try searching for it on e-bay.  It is fairly reasonably priced.)

A console table is a table that usually stands against a wall or behind a couch.  Usually it is long and narrow.  I love these in my real house as well as my Barbie rooms because they fill spaces well and are very versatile.

This is what it looked like before I redid it.  I just took off the back, painted the legs and added the contact paper top.

One of my favorites is this picture frame from the Bombay company.  I took the backings for the pictures and the glass out and have a lovely large table one might see standing in a hotel lobby.

I love this mirrored table I used in the Black and White Room.  It caught the light beautifully.  The top is a piece of round beveled mirror and the base was a vase or candle holder or something.  I'm not sure what because I bought it at a garage sale.

This isn't a good photo of this table, but I included it anyway because I love the table.  If I get time I'll take a better picture for this.  This is just a piece of tile with four wooden legs glued to it. 

Here is another piece of tile on a pencil holder. 

Cute little boxes make great tables.  These look like the real side tables made to look like a stack of giant books. (I've always secretly wanted some of those!)  Here is the miniature version.  The drawers really open, but I haven't decided whether to put on drawer pulls or not.  I planned on using them in a library sometime.  Can't see them as well as I would like in this photo, but they are really cute- another garage sale find!

These last 2 tables are flea market finds.  I don't even know what they were originally meant for, but they looked like tables to me.  The first table didn't quite work in this first pic, so I tried it in a a more exotic setting.  It may end up somewhere ultra modern, though.

Sometimes you can just experiment with anything.  I bought these three marble cubes at a garage sale for fifty cents and I think I'm going to have fun with them!  They would have looked better here with a lamp, but I got lazy.

There are lots of vintage tables I have picked up over the years.  Look for these at garage sales, thrift stores and flea markets.  (You can find them from time to time at antique stores, but they are pricey.)   Several of these are real favorites of mine.

I see these brass game tables from time to time, usually in antique shops.  I love the checkerboard on top.  I usually put little chess figures on it. 

You can find these trinket boxes occasionally.  They have a big, ugly brass rose on top that is completely out of proportion to the table.  You have to remove it CAREFULLY.  No matter what you do, it will tear part of the wonderful faux leather top, but you can set a picture frame or book or something to hide it.

The pictures on the left are real tables and the pictures on the right are one sixth scale versions that are similar, though not exactly the same.