Weddingbee boards

Like bluespurrs said, save on a venue by using either a free space (like a public park or your backyard) or a really cheap space (like a campground). Try to get an outdoor space, because then you'll have to decorate as minimally as possible -- the only catch with this is you either have to be pretty certain of the weather, or have a back-up plan. 

Get stuff for decorating in bulk -- fabric is your friend, flowers are not. Fill borrowed or thrift-store vases with water and whole or sliced fruit, or fill them with rocks collected from around the neighbourhood and stick twigs or a single silk flower in the middle. Instead of bouquets, have your bridesmaids (and you) carry something meaningful to them, or a single long-stemmed flower, or carry nothing at all. 

Try on bridesmaid dresses, thrift/department store dresses, prom dresses, cocktail dresses and sundresses, and if all else fails, have your dress custom-made by a Chinese company (usually $200-$300 with minimal alterations). Have your groom wear a suit he already has.

Check out amazing brides like Miss. Bunny here on Weddingbee ($5K budget), and Sara of http://2000dollarwedding.com for inspiration.

My budget is $5K as well, and this is what we're doing to save money:

Cheap Venue: We'll either be having our wedding at a local campground (about $300), at a local greenspace (free), or our backyard (free).

Few Flowers: We're planning on having very few flowers (two long-stemmed blue roses and about 10 daisies), and the flowers we will be having will be silk, so that we can re-use them as decoration for our house, and as keepsakes.

DIY: We're DIY-ing A LOT of stuff. Our food (make-your-own-sandwich buffet; we'll be buying meats, cheeses, and breads from Costco, along with veggies, ingredients for dips/spreads, and we will probably have salads, hors d'oeuvres, and soup), our cake (cupcake tower that my maid of honour, my sister and I are going to bake and decorate the day before, hopefully), our stationary (including our invites, RSVPs, thank-you cards, programs, etc.; we're going to make all these in my fiance's parents' basement, along with his mother and maybe my MOH, because she has a TON of craft-making supplies), our decorations (instead of buying pre-made battery-operated LEDs to light our paper lanterns, we're making our own "throwies"), and our music (hooray for iPods!).

No Favours: 'Nuff said.

Getting Family & Friends Involved: Getting our family involved is saving us thousands of dollars. My dad will be doing our videography. My fiance's aunt will be doing our photography. My FMIL will be contributing craft supplies for paper goods, as well as our guest book. My MOH offered to make my wedding dress!

Small Guest List: 85% of our (80-person) guest list is family. Parents, siblings, aunts, uncles, cousins (maybe), and grandparents. Then there are a couple close friends we're inviting, and that's it. No co-workers, no lost-lost buddies, no second-cousins-twice-removed.