Folks, we've got a crisis on our hands; one that you've probably heard about already but bears repeating. It's called Colony Collapse Disorder, and it means that honey bees--our top insect pollinators, partly responsible for ensuring that crops successfully produce and bear fruit--are strangely disappearing. They need all the help they can get right now, and there are a few simple things you can do (provided you're not allergic, of course) to help the bees get back on their feet--err, wings. Part of the problem bees are facing, according to books like Fruitless Fall by Rowan Jacobsen, is the lack of flowering plant variety.
Since bees do best in environments that offer great plant diversity, so in addition to the seeds you're starting for your spring fruit and veggie gardens, sow some from this bee-friendly list. Flowers native to your area are best, of course, so ask your local plant gurus (think nurseries, farmer's markets, etc.) what would do the trick.
If your city allows it (check the ordinances), and your neighbors are cool with it, and you're up for the bit of work entailed (yes, that's a long list of pre-recs, but...) look into backyard beekeeping. There is a wealth of information online, of course, but visit the library to find beekeeping books and be sure to read up before starting a hive. We're in the very beginning stages of putting hives out on two family farms, which means we're investigating everything from costs to upkeep to what to do in the event of bee mutiny.
If you want to invite the bees but don't want to keep a hive, look into other bee homes like these, or this one.
And without touching the bees at all, you can help out by supporting your local farmers and purchasing local honey. Not only will it taste like your surroundings (fields of wildflowers or clovers, for instance), but it's great for alleviating local allergies.
Photo by gklinek via sxc.hu.