Many crontab tricks abound, also. The time fields have many methods of specifying time periods. Examples:

#touch a file every 5 minutes, the hard way
0,5,10,15,20,25,30,35,40,45,50,55 * * * * touch ~/file

#touch a file every 5 mins, the easy way
0-59/5 * * * * touch ~/file

#every weekday, touch file, the hard way
0 6 * * mon touch ~/file
0 6 * * tue touch ~/file
etc.

#every weekday, touch file, the easy way
0 6 * * mon-fri touch ~/file

#one last example, every hour between 6-10 on the hour and 4
0 6-10,4 * * * touch ~/file

So there you go. These help one save a lot of time when setting up crontabs and also allow you to look super elite around all of your unix hacker friends.