Congratulations!
We had a small-ish wedding (90 ppl) and stayed within our budget. We had a rule that we would only invite our closest family and for friends, they had to be people we BOTH had met. If I had some far-flung girlfriend he'd never met, she wasn't invited. Don't, however, try to save money by imposing a random "age cut-off." I know one couple who didn't want children, but had a cousin who was 10 yrs old. They didn't invite her because of her age and my Aunt is STILL bitter 15 years later. Establish your guest criteria, and stick to it. Its easier to be able to say to co-workers and distant relatives "we're only inviting first cousins" etc. Don't invite anyone you would feel weird contacting if they don't RSVP. (And trust me, even within your closest circle, people won't RSVP. Don't ask me why.)
To save money:
1. Have only one person stand up with you and one with your fiance. Less bouqets to buy and you don't have to worry about buying your maid of honor dress at a bridal store. That's really more a cost saver for your maid of honor... I'm sure she'll appreciate it.
2. To stretch flowers at the reception, I made my own centerpieces using a tall clear glass vase, a large colorful flower in the bottom, and small floating candles on top. We then put four votives around the bottom of the vase and had the florist spread rose petals around the center of the table, in between the votives and the center vase. Although I wanted really lavish flowers, it actually looked pretty good, and some of the guests took them home and still have them on their mantle! This was all stuff that was inexpensively bought at either craft stores or Ikea. We spent more to get nice table linens, which was worth it. Your table linens will be in a lot of your reception photos (believe it or not!)
3. Buffet style is less expensive than plated, if you go for an inside wedding.
4. If you can choose a venue where you are allowed to bring in your own caterer, odds are it will be cheaper, and possibly BYOB. Make sure you have the skills to track all this stuff down and keep it organized. If you don't like to "party plan", you'll be better off choosing a hotel where they will do it all for you. Try a Friday night and NEGOTIATE. Unless you want a Saturday in June, you shouldn't ever have to pay full price. Also, consider an "out of the way" hotel: my girlfriend choose a hotel at the Philadelphia Airport, which doesn't get a lot of group business on a Saturday night. She got the whole shebang (ceremony and reception) for a song.
5. No one will care if you skip the champagne toast or just serve well drinks or one kind of beer. Unless you're non-drinkers, though, do make sure you have plenty of whatever you're serving. But if most of your friends are beer drinkers, just have beer and maybe some wine with dinner.
6. You can definitly print your own invitations, as long as you have those kind of skills. If not, go to an stationery store and be clear about your budget. There are many, many affordable options. (I used to work in a stationery shop.)
To splurge on (or not cheap out on):
Personally, I think the music is CRUCIAL. We went to a very extravagant wedding at a museum and because they don't like "DJs" they just had a play list on their iPod. It was terrible. Even if you don't like DJs, they provide a structure for the reception and keep everything moving. I don't think you need to hire a band, but please, please hire a really GOOD DJ. I think even if the food is just so-so, if people can have fun and dance they'll have a good time. Even if you have it in your backyard (which can be really fun!), hire a good DJ!!!!
Don't skimp on the photographer (as many have said) but if you're not really pressed about a videographer, just have a friend do it.
Don't rely too much on friends, close family for set-up, clean-up etc. I think if you treat everyone like an invited guest its better and there won't be any bad feelings later. Its worth money to have it someplace where no one has to sweep up or do the dishes at the end. Even if you do the backyard, hire someone to help out and serve/clean up.
Do not under any circumstance, buy disposable cameras for the tables. That is really past its prime. People waste them. Plenty of people will have their own cameras and get great shots to supplement your professional photographer.
Most importantly, though, you and your fiance need to think about what is important to YOU. If its flowers, spend the money there and cut back elsewhere. If its a wedding video, likewise. If you don't care about the cake, have someone make it. For me, it was my bouquet, I spent a pretty penny on it and it was so worth it. It was in almost every picture! But, if you don't care about that, there are a thousand ways to cut prices there... even just carry a single rose or calla lilly. (or silk flowers, or a Bible, etc.)
I wish you all the best. It feels really good to walk-away from a wedding with no looming charges on your credit cards... resist any temptation to overspend.