How can I list post from many catalogs

I want to get the post from all of my catalogs,and list them on my homepage,like bellow:

|————-|
|___catalog 1_|
| 1.post1 |
| 2.post2 |
| 3.mypst |
| 4.mmmm |
| >more |
————–
|————-|
|___catalog 2_|
| 1.post1 |
| 2.post2 |
| 3.mypst |
| 4.mmmm |
| >more |
————–
|————-|
|___catalog 3_|
| 1.post1 |
| 2.post2 |
| 3.mypst |
| 4.mmmm |
| >more |
————–

so how can I loop all of my catalogs,and in the loop,how can I get the contents?

thanks !

What I want to know is how to loop out the data from a specified catalog,which I know the cat id!