I took two serving tables and made two vanities. I kept the original wood top and if it starts looking bad I will replace with granite. The issue will usually be depth and drawer placement. You need at least 18" inches in depth and thats tight and of course drawers that allow for sink. The serving table had doors at center and open space below which gave room for sink and made a great place for baskets.

Staceyneil did this for her daughter's bathroom. Well maybe it was more of a chest than a dresser but it turned out beautifully.

You might be able to find some pictures here but I bet Stacey will pop in.

ALso look up my3dogs house. She posts on the decorating forum so may not check here. She has marvelous examples of vanity conversions as well as lots of other beautiful details.

Hi lavender,
Yes, I just did this in my daughter's bath. It's a lot less modern than my usual style (we let her have a lot of design input) so we used an antique dresser. We modified it in the following ways:
1)removed the original wooden top and replaced with a piece of quartzite from the "exotics" remnant stack at the local stone fabricator. I tested chunks of various stones and found this one to be quite impervious to staining and etching by everything but salicitic acid...
2) Reworked the top two drawers and center stile to accomodate the sink plumbing but still allow useable drawers.
3) Added modern under-mount drawer glides to all the drawer so that they'd be easy for her to use.
4) attached the dresser securely to the wall
4) Painted the dresser (it had previously been painted, otherwise I would have left it wood) and added vintage crystal knobs.

Another idea for the top, if you don't want to use stone, is to simply varnish the existing top. We have a mahogany top in our master bath (with overmount sinks) and we just used floor poly on it. It's holding up great!

Couple thoughts: when you're shopping for the right dresser, keep height in mind. I looked at several that were either too high (no a big deal, I would have cut the legs down a bit) or too short (would have had to build up the top more OR use a semi-recessed or vessel-style sink). The sink you choose will totally influence the height. A vessel or semi-recessed or drop-in sink will be easier and cheaper to do, especially if you choose stone (you won't have to pay for a polished, finished cutout.)

That right there (and the other project) is why staceyneil is one of my heros. I'm doing two custom vanity projects for the new house, including one conversion from a dresser to a double vanity (we're a few months away from actually installing it though). Some of the other projects that I drew inspiration from were brutuses and checksplay.

Two threads to read:

With Brutuses
With Checksplay

We're not doing a stone top since the whole point of our project was to cut cost. Our double vanity costs under $200 for an old dresser, stain, poly, new legs and sinks. Our downstairs single I ended up building a cabinet to fit our craiglists find sink.