Family Finder Testing, or Autosomal DNA Testing, is on sale for $199. You save $90. Anyone can take the test. If your parents or grandparents are still living, you will want to test them also. This is the same kind of testing done at 23andMe (currently not on sale for $299) and the "new" AncestryDNA.
AncestryDNA is running a sort-of sale, more like an incentive to buy the DNA kit and subscribe to the records available at Ancestry. For a more complete analysis of the fee structure, please see CeCe's post.
For those of you researching a particular surname, you can purchase a Y-DNA kit for a man in the direct male line of interest to you. Also on sale. The more markers, the better.
Ancestry.com's Y-DNA services cost more than FamilyTreeDNA at this moment. Once your DNA is computed, you can upload the results to other sites, such as Ysearch, in hopes of finding matches who tested elsewhere.
For those of you tracing your family trees without the assistance of DNA, now is a great time to get started with the scientific analysis of your roots.