Both Family Tree DNA ($89) and AncestryDNA ($79) have Christmas sales for their DNA kits (those prices do not include shipping). I think the Ancestry.com DNA testing sale will last only until November 20th. Family Tree DNA‘s sale is on until the end of the year. In contrast 23andme just doubled their price but is adding new interfaces and health results.
Family Tree DNA has special gift coupons for existing customers; so log in every week and see what you have. Roberta Estes suggested that people could put their unwanted codes in the comments on her detailed post about the ftDNA sale. That seems like a good idea to me. You can do that here too, but please indicate in a reply to each coupon comment when you have taken that one. I will list a few of my coupon codes also.
I have written up my recommendations for where to do your DNA testing on my comparison page. Here is a summary of my current thoughts on which company to use.
I prefer Family Tree DNA for testing very old relatives since it is a cheek swab, not spit, which is far easier for many. Also you will find more matches there than at ancestry if you have non-American or ashkenazi ancestors. Ancestry.com is best for those with colonial ancestry. Use 23andme if you want the health results or are adopted so are testing everywhere. It currently has a larger database for Europeans than either of the others so if finding relatives across the pond is important to you, that is also a reason to test at 23andme. Note that the raw data from ancestry can be uploaded to Promethease.com to get many of your health results but ftDNA deliberately does not include health SNPs. For just $39 more, you can do both ancestry and Family Tree DNA by testing at ancestry then uploading to Family Tree DNA (see my post on that).
Wherever you test, consider uploading your raw data to GEDmatch.com in order to get some different and probably better ancestry composition results, as well as to be able to compare your DNA to people who have tested elsewhere. Also upload your results to DNA.land which may have some interesting tools in the future.