The community surrounding us has the most vested interest in helping you than any organization or agency you can find. You probably have noticed that if you type in the word grants in a search engine you will be met with a gazillion pages. Most of these pages refer to other pages. There are hundreds of books on grantmaking as well. The best way I know how is to think of grants as projects.
Projects have a beginning, a middle, and an end.
Try my Top Tips for Successful Fundraising posted in the resource area. I've found that most national companies have some sort of giving programs, and although they may not spell it out on their Web sites, you can gain a ton of information about the company on the World Wide Web. NEC, Packard Bell, and Intel are literally in my backyard. You begin with a letter of introduction to the CEO or president of the company. Then you follow up with a phone call and try to get an appointment.