It's kind of a commitment, but maybe turn them into terrariums?

how about some crocus bulbs. My favorite first sign of spring.

Little bird's nests with tiny eggs, (can often find at craft stores, but also at little gift shops) or maybe some kumquats. What about making them little terrariums, with soil and a tiny succulent.

I agree with the terrarium suggestion.

Pine needles and eggs to make a nest? Turn them into a terrarium with moss? Fill with paper mache painted eggs (look up Kashmiri painted eggs)?

Another vote for terrariums!

These are some things I'll use in spring/summer: lemons, seashells, dried moss/dried moss ball things, an actual plant for a terrarium of sorts, and paler stone vase fillers.

This site has some nice ideas:
http://livingwithlindsay.com/2009/04/ten-fantastic-fillers-for-apothecary-jars.html

I actually have a similar question except...what do you do around this time of year? It's snowing like crazy here (midwest) and going to be wintry for a while so I'm not feeling springy. How do you seasonally change out vase filler stuff for winter without evoking the holidays (mine are currently still filled with ornaments and evergreen clippings because I just don't know what to do with them until spring!)

Living moss is low maintenance, pretty, and biodegradable.

Where I live, in early Feb the early wildflowers (weeds) crop up any old place, and some wild violets or even the humble dandelion on display could herald the new season and provide an examination of the process of flowering.

Wheat grass (grown from wheat berries) is outrageously easy and beautiful, although short-lived. Grows lush in one week, stays so for maybe one more week, then you can just start over. They don't need much at all to germinate, just some moisture and their own internal food supply.

For Spring - I love the idea of eggs and moss - here are a couple of photos:

http://1.bp.blogspot.com/_jkMcMDTZ3p0/SsTnzjbAGKI/AAAAAAAABiU/qTqJdray4Y4/s1600-h/apothecary.romantichomes.bmp

http://2.bp.blogspot.com/_jkMcMDTZ3p0/SsTn4rX5IGI/AAAAAAAABic/IFQettieG3E/s1600-h/apothecary.amazon.com

And for Summer - shells!!!

Some pretty rocks/sea glass, maybe a little moss, and force some daffodils or crocus bulbs.

Force some branches! There's a tutorial here:
http://designpopinteriors.blogspot.com/2011/01/spring-will-be-here-in-three-weeks.html

I found some fake hydrangias and mixed them with fake lemons and green apples in my jars. Very spring-like. Easier to clean and swap out when the seasons change than stuff involving real dirt.

Crocus bulbs would be gorgeous!

you could force one amaryllis or a few paperwhite bulbs per container. the high sides would keep the bulbs from flopping.
http://www.theplantexpert.com/springbulbs/Forcing.html

When is Spring coming?

@ RNM - I'm in the Midwest, too. I usually buy fresh bamboo and small houseplants at this time of year to freshen things up. I shouldn't admit this, but they usually go outside during summer, then I forget them until after the first frost. Then process starts all over again. Well, it's cheaper than cut flowers...