As most of you know, the smallest time a cron job can be configured to run is every minute.
To run a script every 15 seconds for example, you could use the following:
main cron job:
* * * * * /path/to/wrapper.sh
wrapper.sh:
/path/to/script & sleep 15 /path/to/script & sleep 15 /path/to/script & sleep 15 /path/to/script &
If you can suggest any nicer alternatives to this example, please let me know. 
