"Have a look at the rules in the Book of Numbers. When was the last time you obeyed God's orders to offer animal sacfrifice? What, you forgot to do that last week? (You can find lots of things like this in the Old Testament). People will overlook old societal rules like this, yet extract bits that they rather like such as homosexuality being an abomination. "

The rules for animal sacrifices are in Leviticus. Those from the tribe of Levi(specifically the Kohanim("Priests" those whose father was a Kohain. The first kohain was Aaron, Moses' brother) with the assistance of of Leviim(those from the tribe of Levi who were not Kohanim) assisted in the Temple duties. Animal sacrifices ended with the destruction of the Temple in 70 CE.

There are 613 commandment in the Old testatament that Jews are commanded to follow, and 7 commandments(the Noahide Laws) which were given for all humanity to observe. These are the 7 Noahide Laws.

1. BELIEF IN G-D
Do not worship Idols
2. RESPECT G-D AND PRAISE HIM
Do Not Blaspheme His Name

3. RESPECT HUMAN LIFE
Do Not Murder

4. RESPECT THE FAMILY
Do Not Commit Immoral Sexual Acts

5. RESPECT FOR OTHERS’ RIGHTS AND PROPERTY
Do Not Steal

6. CREATION OF A JUDICIAL SYSTEM
Pursue Justice

7. RESPECT ALL CREATURES
Do not be cruel to animals.

http://www.noahide.org/

As for the 613 commandments the Jews were given, many don't apply now since they deal with service in The Temple(The second Temple in Jerusalem was destroyed in 70 CE). others deal with special regulations for produce grown in Israel. Some of the commandments are only for men, while others are only for women. Orthodox Jews follow those of the 613 commandments that are applicable to them.