[Here | There] [I / you / he] goes. It can be used in a number of ways. At the start of an activity: "Have we got everything? The keys, money, bags? OK, here we go!" It can be used to point out something happening right now: As horses in a race pass by, you might say "There they go!" Or to the police, pointing out a robber running away down the road: "There he goes!" It can also be used sarcastically. "There he goes, asking for someone else to pay the bill again!" "There you go again" was famously and repeatedly used by Ronald Reagan to denigrate President Jimmy Carter during the 1980 United States presidential election debates. See Wikipedia: http://en.wikipedia.org/wiki/There_you_go_again

There you go, here you go, can both me used in the sense of "here you are" when handing someone something,

Mother: I want you to walk to the supermarket and buy some lobster for tonight's dinner. James: I don't want to. I want to stay home and watch TV all day. Mother: I really would appreciate it if you would do this for me. James: Well, OK, I will go because I will get some exercise by walking and I will be helping you prepare a delicious meal for me. Mother: THERE YOU GO! ( = That's the way to think!)

The previous answers are very good. There is another way we use "there you go" though sometimes. Sometimes you can use "there you go" in a situation to comfort someone. For example: "My cat is missing!" "There you go, it's ok. We will find him."

On top of the other answers it can also be used to show that something has been found. Two people are looking for information on the Internet. One of the finds the info and says to the other person "here you go/here you go/there you go" each one would work in this example. Or simply when something is found. "Mum, I can't find my key." Mum looks around for the key "there you go, I found it on the table"