The largest and, in our opinion, the best genealogy DNA testing and tree-matching service. Some may disagree, but if you have a tree to work and a lot of relatives who want to watch, it cannot be beat. Their iPad/iPhone app is awesome. Autosynch with the new version of Family Tree Maker software allows you to prune and graft off-line/locally and synch up at any time.
AncestryDNA is attractively priced and results can now be compared to ftDNA and 23andMe autosomal DNA data by uploading raw files to GEDMatch [an absolutely awesome free DNA database and comparison tool], DNA.land [ a free research database], MyHeritage and even to FamilyTreeDNA [limited reporting is free; full for $19]. After years of not committing to a favorite or 'best' recommendation, AncestryDNA with its incredible tree-matching algorithms is now clearly our go-to choice for DNA-Assisted genealogy. [CLICK HERE for the reasons why as wriiten in an e-mail to a recently 'found' cousin of my wife]
Our 'dream team' would still be for Ancestry.com to buy GEDMatch, or offer the same import and analytical functionality, and combine it with Ancestry's incredible databases, software, and tree-matching expertise... ed.
Family Tree DNA (ftDNA)
Y-DNA testing to 111 markers, and SNPs, full-sequence mitochondrial mt-DNA, new autosomal "Cousin" testing/matching with extensive help, FAQs, Forums and Projects. DNA is what they do... You can upload raw data from Ancestry (or older 23andMe kits) to FamilyTreeDNA [limited reporting is free; full for $19].
23andMe - DNA
Health-related focus but you get all that PLUS comprehensive Autosomal and ancestry testing/data as well. Genealogical/autosomal results are compatible with ftDNA and GEDMatch and can be uploaded for free. If health markers are your thing, 23andMe might be for you. UPDATE: 23andMe's latest tests are NOT uploadable to FTDNA, but GEDmatch has re-tooled to accommodate.
R.M. Cousins Genealogical Services
Peggy, the primary researcher, lives in DC and travels into the city for a very nominal fee. Her primary target is the National Archives where she has demonstrated wizardry with Civil War files. If you have Civil War vets or pensioners in your tree, and have not explored the Civil War soldier and pension files, treat yourself...