Any that I have personally tried and can vouch for are marked with a star.
PLAY SPACE FOR CHILDREN
FITNESS
*Fit4Mom: Offers classes like Stroller Strides and Stroller Barre for moms with their little one using the stroller and engaging the kids throughout the class. I personally participate in the Vienna/Falls Church group and love it! They have a maternity plan that allows unlimited classes for two months, which is great while you're on maternity leave! Website: http://fit4mom.com/
Moms Run This Town: Running group with one chapter in Herndon/Reston. Website: http://momsrunthistown.com/herndonrestonva/
Beloved Yoga: Located in Reston, they have Mommy/baby yoga classes and you can meet mommies there. The instructor is wonderful and has sponsored free mommy/baby days in the past for baby massage, sign language, etc. Website: http://www.belovedyoga.com/
Sun & Moon Yoga: Locations in Arlington and Fairfax with prenatal and mom/baby yoga classes. Website: http://www.sunandmoonstudio.com/
CLASSES
Reston Community Center: Reston Community Center has fantastic baby music and swim classes where you can meet other moms. If you are a Reston resident or employee you pay the Reston rate too. Website: http://www.restoncommunitycenter.com/
*Fairfax County Parktakes: Classes that range from swimming, to camps, to cooking, to dance, etc. Cheaper for Fairfax County residents, but open to anyone. Website: http://www.fairfaxcounty.gov/parks/parktakes/
NoVA Playlabs: NoVA Playlabs in Chantilly offers play space for children, including classes like baby sign language. Website: http://www.novaplaylabs.com/
PLAY SPACE FOR CHILDREN
Chibis: Chibis' (pronounced: CHEE-bees) mission is to provide an Open Play environment where parents can have fun with their children or socialize with friends while their children enjoy our fun, safe, CLEAN playground. Personalized parties & private events are also their specialty! Website: http://www.chibisindoorplayground.com/
Busy Bees: This play area is located in Falls Church. Adults and children under age 1 are free and there's free coffee/tea and wifi! It's $15 and you can come in and out of the facility, the fee is good for the entire day. Website: http://www.busybeesplay.com/
*PB & Jack: This play area is located in Fairfax. Note that no outside food is allowed so they can keep the facility 100% nut free. Website: http://www.pbandjack.com/
CONSIGNMENT/HANDMEDOWNS
*Dulles Reuses Baby Items: This Facebook group allows moms to sell - or sometimes give away - baby gear (e.g., swings, sound machines), baby clothes (up to 2 years), and maternity clothes. Website: https://www.facebook.com/groups/388460154524424/
Consignment Mommies: Website listing consignment sales near you. There are some huge spring ones at Dulles Sportsplex and in Ashburn. Website: http://consignmentmommies.com/
Swap.com: According to one neighbor of mine, the quality is outstanding. Website: www.swap.com
Freecycle: You can sign up for our local freecycle chapter. People give away baby clothes & supplies daily on it and it's a great free resource for things. Website: www.frecycle.net
BREASTFEEDING RESOURCES
La Leche League USA: There is a national Facebook page and local chapter Facebook pages. Websites: https://www.facebook.com/LaLecheLeagueUSA/
La Leche League Herndon/Reston: Our local chapter has open meetings every Tuesday from 1-3pm at the Starbucks in Fox Mill. Website: https://www.facebook.com/La-Leche-League-of-Herndon-Reston-PM-161853187215480/?fref=ts
*LLL Mother-to-Mother Forums: I found this group INCREDIBLE when I was nursing and didn't have enough people to get advice from. You can pose questions and get multiple perspectives, and you can share the information you've learned. Website: https://www.facebook.com/groups/LLLI.Breastfeeding.Support/?fref=nf
BLOGS/WEBSITES
*Dulles Moms: They cover every topic imaginable! Website: www.dullesmoms.com
*Super Healthy Kids: This site has fun recipes and food ideas for families with kids. Website: http://www.superhealthykids.com - Facebook: https://www.facebook.com/superhealthykids/
*A Mighty Girl: I love this website for it's great powerful stories about women and girls. It also provides books and movies that help demonstrate how "mighty" girls can be by age level. Website: http://www.amightygirl.com/ - Facebook: https://www.facebook.com/amightygirl/?fref=ts
OTHER
Baby Wearing: There is a DC baby wearing chapter where you can "borrow" baby carriers and slings from their carrier library and meet other mommies that way too. Website: https://www.facebook.com/BWIofDCMDVA