The first flowers in my garden a couple of weeks ago were yellow and purple crocus and the tiny, pale blue star-faces of chionodoxa, aptly nicknamed glory-of-the-snow.
These tiny bulbs often sprout even before the snow is gone. I planted maybe 20 glory-of-the-snow bulbs a decade ago. By last year I had hundreds near the garage. They came up through cracks in the railroad-tie garden edge and sprouted from the lawn. Mixed with dark blue Siberian squill, another little bulb that blooms early, they have never failed to tell me when spring is really here.
Here's some more information about my favorite early bulb:


http://www.theplantexpert.com/springbulbs/Chionodoxa.html


Right on their heels is Tulip tarda, a mini-tulip that reaches about six inches high. The star-shaped flowers open wide during the day, showing off bright yellow flowers edged in white. They, too, seem eager to take over a garden and I've been happy to let them do that.
When my rotting garage was replaced last year, the only thing I regretted was that there was no way to rescue all those beautiful bulbs in midsummer. Their leaves had shrivelled and they were invisible again, waiting for spring. I dug up some bulbs and replanted them in other gardens. But there was so much work to do to reclaim the construction area that finally I just filled a couple of pots with dirt from that area, hoped there were some bulbs there and then forgot about them.
The pots sat ignored for the rest of the year, one under a tree, the other stuck behind the compost bin. When I spotted them this spring they were bursting with soon-to-bloom glory of the snow, squill and tulip tarda.
I've transplanted forced hyacinths from their pots into my garden and had them come back for many years, but one bulb that I don't add to my perennial garden is the Easter lily. You can plant the lily if you want and they will return for a few years, but the plants carry a virus called "lily symptomless virus" that can spread to other lilies. You can read about it here:
http://www.extension.umn.edu/projects/yardandgarden/YGLNews/YGLNewsApr12007.html#easterlily


Do you have a favorite bulb, or tricks to get them to come back year after year?