I have tested my autosomal chromosomes at both 23andMe and FTDNA.
At 23andMe in Relative Finder I have 464 people with matching chromosome segments. My largest match is with my 1st cousin at 19.79% of our DNA. Most 1st cousins will be around 12.5% but we share 6 of 8 Great Grandparents so we have more matching DNA than most 1st cousins. The lowest amount of DNA I have with someone is .08% and that was the first person I was able to find a match with as 10th cousins once removed. 106 people are currently sharing genomes with me which allows us to see on which chromosome we have a match.
The majority of my matches are on one or another of chromosomes 1 through 22. However I have 9 people who have 10 shared segments with me on the X chromosome which, as a male, I inherited from my mother. By mapping the start and end locations of the shared segments I can see who may share a common X ancestry with me or with each other. In this case my 1st cousin shares 2 segments with me and 1 of those segments with me and two brothers. I partially share a segment with a mother and daughter and 3 other persons. And one of those persons shares half a segment with another person.
When males share an X segment it means they are related through their mothers' ancestry. When a male shares an X segment with a female they can be related on his mother's ancestry and on either her mother's or father's X ancestry.
Unless one or both of your parents also takes the 23andme test, it can be difficult to "phase" your results, in other words, to be able to assign a segment to your mother's or father's ancestry. Until this can be done, you can't know if two people who match you at the same location match your segment strand from either your mother or your father. This means that you can't say that it means they have the same ancestry to each other as they have to you. If your parent's are deceased, you may be able to phase your results by testing siblings of you or your parents.
I have definitely identified 6 relationships at 23andMe. Over 50,000 people have tested at 23andme in the past two years.
At FTDNA in Family Finder I have 53 matches. Because FTDNA didn't start Family Finder until recently, the number of matches is much smaller than at 23andMe. However, since Family Finder only tests for ancestry, it is believed that the people testing will be more knowledgeable about genealogy than those at 23andMe. So far I have also identified 6 connections at FTDNA, the same as at 23andMe but twice as many per number of sharing matches. At this time FTDNA does not show matches on the X chromosome but it has said it will do so in the future.
I have also had autosomal testing done with Sorenson Molecular Genealogy Foundation but they have not yet released their results. They have tested over 100,000 people and have pedigrees attached to most of those.