Supplementing (and expanding) on Gershon Gold's ideas, here's what I think has worked in my shul:

• High Holiday seats, believe it or ot, generate a huge part of our shul's annual income. You may think this is "internal", and for the majority, it is. But, our shul has advertised its services in local (and neighboring community) newspapers as well. Also, regular members bring in their family members and friends, and the y spread the word to others that our shul has a great chazzan, friendly environment, and many of the members pay for their friends' seats - often even if they don't show up! (I don't get that idea, but it happens somewhat. Who cares? The shul is getting money for empty seats.) On Yom Kippur, the extra crowd also generates more income into the annual
• Yizkor appeal - Boy, is this a huge revenue maker! And much of this money is coming from the extra guests, too!
• Along with Gershon's suggestion of guest lecturers, which we sometimes have, the majority of the lectures are run by the rabbi, himself. He is good on using contemporary books and discussing controversial current topics and giving it a Jewish "twist". These events are well advertised, and some of them generate extra income.
• Tap into your own shul's talent, both past & present. Our shul has been around for 85 years, so we've had many interesting noteable past members. Allan Zweibel was one of the major writers for Saturday Night Live. SInce he was a former shul member, they asked him to speak about his career and do a few comedic skits. $75 a ticket to see him and have a small buffet! About 300 people showed up. Plus, he sold some of his books and the shul got a percentage of his sales. Not bad for one night!
• Jews may not necessary like to cook, but it seems that they love to eat, esp, if someone else makes the food. And, if the food is delicious, they want to know how you made it. It does take some effort to compile a cook book from your members. But, with computers and email, etc. the process is not too hard. You need 1 or 2 editors and some clipart / pics, and you can get a great cookbook together pretty quickly. It will sell quite well!
• Education is a huge income source, esp. if you can get lots of kids. Our shul has 5 different "schools" from the "traditional" Hebrew day school to special schools for mentally challenged, Israeli kids, Russian kids, and a few others. Most of the kids come from non-members. I hate to say it, but there are more kids attending school than adults attending most of our Shabbat services! We could use a few of them!

You didn't describe the demographics of your synagogue, so I can't say how much of what I listed would work well for you - esp. the education area if you don't have a lot of young families / kids. Nonetheless, even if you are dealing with a 70+ congregation, if you have a creative and savvy few people willing to coordinate a regular program, you can cater to them, Our shul runs a "senior" midday program a few days a week. On its own, it doesn't generate income and costs the shul a bit, actually, since they provide free light lunch to about 50 regular attendants. But, word of mouth is the best advertising, I think. The seniors tell younger people what a generous shul we have, and outsiders become members or they end up donating money to defray the cost of the program.

Here's a "crazy" idea. Some shuls know the art of attracting the "big machers" - the people with the big bucks. That's what you really want! I know that you live in Pittsburgh. They have a number of major shuls and yeshivot that are successful. Perhaps, you can contact the executive director or chief fund-raiser for some advice?

Good luck to you. I know that raising money is very challenging!