When it comes to bubbly (the term I use for sparkling wine) there are plenty of options; virtually every winemaking region makes a sparkling wine. Walk through a wine store and you'll see Prosecco from Italy, Cava from Spain, Sekt from Germany, sparkling wine from California and Australia. (There's even a fabulous sparkling wine from New Mexico from Gruet Winery; it's around $14). What sets these apart from true Champagne are the winemaking methods and the grapes used; Champagne is made in the Champagne region of France from three grapes using the Methode Champenoise, while other regions don't have these restrictions.
When I can't get the real stuff (Champagne) I look to the other wine regions of France; they make lovely sparkling wine from a variety of grapes. These are luscious, lovely sparkling wines that give you a bang for your buck. My top three favorites are Lucien Albrecht Cremant d'Alsace (from the Alsace region; around $20), Louis Bouillot Cremant de Bourgogne Rose (from the Burgundy region; about $14), and J. Laurens Brut Cremant de Limoux from Southern France; about $13).
Before you shop for bubbly think about how you're serving it. Always get better quality bubbly if you're serving it straight up. If you're simply serving mimosas you can get away with a less expensive bubbly like an $8 Cava or Prosecco. (Don't waste good bubbly by adding orange juice!)
Finally, when you open that bottle at the next holiday party you can dazzle everyone with this quote from Lily Bollinger, who was asked when she drinks Champagne:
I only drink Champagne when I'm happy, and when I'm sad.
Sometimes I drink it when I'm alone.
When I have company, I consider it obligatory.
I trifle with it if I am not hungry and drink it when I am.
Otherwise I never touch it - unless I'm thirsty."