Import and Export database in Mongo just like MySQL
If you look inside mongodb/bin folder (ls -l)
You can find a couple of binaries.

The mongoDB has import and export tools. 

If you're running mongod locally on the default port, you can just do:

$ ./mongodump


Example: Dumping Everything

$ ./mongodump --host prod.example.com


Example: Dumping a Single Collection

$ ./mongodump --db blog --collection posts


Others like

mongoexport, mongoimport, mongorestore, bsondump etc.

for more http://www.mongodb.org/display/DOCS/Import+Export+Tools