I love the DIY feel and laid back vibe of chalkboards in weddings.  You can use them for so many different things, and can “dress them up” or keep them low key.  Here are some of my favorite uses:

To display seating assignments, in lieu of escort cards:

As Escort Cards:

Drink or Signature Cocktail Menu:
For messages for your photo booth guestbook:

To explain your photo booth:
For Menus or games:
Top:  Sarah K. Chen, Bottom:  Via Once Wed

For Various Wedding Signage:

Bride and Groom signage (for photos, thank you cards, etc.):
To explain a tribute to a loved one (and I love this tribute idea):

As table numbers:

The table number above is also a great DIY project.  Find candle holders that have a smooth surface.  Paint them with chalkboard paint (available at any craft store).  Once the paint dries, you can write the table number in chalk.  Put in a candle, and voila, DIY candle holders / table numbers.  LOVE this idea!
What are your favorite chalkboard uses?