It's probably time to hang up a shingle and promote yourself as a freelancer, at least for the time being. Acquent is one good place to start. Make yourself a fantastic-looking business card, carry everywhere and give out freely.
Although you can always poke around for pro bono work for local charitable or religious organizations, these aren't the best for building a portfolio. You can more profitably (in both senses of the word) find work by surveying your local area and finding small to medium sized companies with awful identity designs and just dropping in to see the owner(s) with a proposal to revamp their look for a modest-but-not-too-modest fee. A complete identity program or a coordinated series of ads says far more about your abilities as a designer than a collection of one-off pieces.
Local performing arts or music groups that don't have good design expertise are also good places to promote for work.
Your approach should always be in the "what can I do to help you be more successful?" vein. Not everyone will bite, and in some cases you won't want to take them on board after meeting them, but with some legwork and a little persistence you'll have a steady trickle of work that you can turn into a good portfolio.
Make sure everyone you come in contact with knows you're a designer. Get in touch with your local InDesign and Photoshop user groups, and ask those folks. Situations where a small design shop needs extra hands come along, and you can make a reputation for yourself by being the heroine of some huge production crunch.
At this stage, it's all about finding lines of communication to people who need design, finding out what they want and tailoring your delivery to the market.