Many of the people who responded to this post said they kept organized by filling a binder with printed materials about vendors and services, plus signed contracts. One said she organized the binder with tabs labeled for each of the major vendors one can expect to hire.
I haven't kept a binder. I've stuffed a bright green folder with contracts and to-do lists that I've ripped out of magazines. I also make a copy of every check we write to book a vendor so I have record of it. I also never go to an appointment without my copy of Today's Bride because the very back of the pub provides lists of questions to ask any given vendor.
As for finding vendors in your price range, many photographers share their rates upfront, one recent bride said, and other vendors will provide quotes if you ask. She recommended -- and I can speak from experience that this is important to ensure you receive an accurate quote -- that brides and grooms share their event's approximate number of guests, location, time and date when asking.
A sorority sister of mine also noted that she's found vendors through bridal shows. As has happened a few times, it's surprising how often I re-read the replies to these questions only to find that they have a timely relevance to my current planning. I just booked a hairdresser and makeup artist I met at the Boutique Bridal Bazaar, where my sister and I showcased our own company, Story of Your Life. (*Like* us, please!)
A few people also noted that they used Excel to do their budgeting. I personally have a piece of paper with three columns: 1) the service being paid for, 2) the amount we've already paid and 3) the amount we have yet to pay. Either, I'm sure, works. It's staying organized that's important.
Finally, one recent groom (yes, sometimes grooms answered these!) recommended delegating projects you can to others. I haven't done this much, but I am working with two wedding planners to whom I will delegate a most important role: coordinating the biggest day of our lives.