Using save the date cards is the easiest and best way to let everyone know of your upcoming festivities.  They can be fun and whimsical or lavishly elegant, what ever suits your tastes, budget and wedding style.

You can find save the date cards that match your invitations or use ones that showcase your wedding.  Beach, tropical, winery, flower themed (and many more) are available from the different invitation companies.

A couple fun alternatives are save the date magnets and photo save the date cards.  They can be personalized to suit your wedding theme.

Be sure to send the cards out 4-6 months ahead of time (or more if you have it).  This will give your guests plenty of time to make arrangements for time off of work and to find the best prices for travel.