I work for the newspaper, and one of my jobs is organizing the community calendar of events, and the community briefs section. I always keep a lookout for fun things to do in the area that are free or cheap (for instance, we have a wine walk every month that’s $10 a person, and loads of fun. There’s also tons of free concerts). We’ll go by ourselves or with friends or family. This is my general suggestion to everyone who is bored - check your local newspaper or city Web site.
My husband and I love video games, so we’ll play a lot of games together - either we’ll get a game that has two-player (our favorite is SSX-3) or we’ll watch each other play the game and occasionally hand it off and let the other continue.
I don’t think this helps because of where I live, but occasionally we’ll each take $5 and go play nickel poker at a local casino. It wastes time and the casino usually has live entertainment and free drinks.
We watch a lot of movies.
Every payday we buy one item of camping gear, be it cookware, candles, a camp stove, or a tent. We’ve amassed a large quantity of camping gear. Occasionally for weekends we’ll go to a campsite, alone or with friends, and just chill out. It’s fun, especially on three-day weekends.
He loves using his hands, so he’s always making things, whether it’s improvements to the apartment (he just put up shelving I’ve been wanting for a while in the kitchen) or just neat stuff, and often times I’ll help.
We also play with the cat. Sometimes this brings great joy to the cat, and sometimes, great chagrin.
My parents live in town, so we usually go over there for dinner once a week, and everyone watches a movie together.
And of course, there’s always sex. 
~Tasha