On my system (ubuntu 10.10) the crontab -e opens up a menu to choose the shell from and it works fine.
By the way, I hope you understand what the command does ?!
It creates a crontab file for the user in the /var/spool/cron/crontabs/ folder and the file has the name of the user
The main or system level crontab file is the /etc/crontab file. So you may directly edit it using gedit or vi or nano or emacs. Warning :- Do this only if you know what you are upto.
If you are trying to create and execute a script to do a cron job :-
In the /etc directory you will probably find some sub directories called
'cron.hourly', 'cron.daily', 'cron.weekly' and 'cron.monthly'.It will be run either hourly, daily,
weekly or monthly, depending on the name of the directory.
Plz check out this nice link
Hope it helped