QuickBooks by Intuit. Intuit does a great job of understanding the needs of small businesses, and the cost of its software won't take a huge bite out of your startup budget.
Peachtree by Sage as well. Peachtree has been on the market a long time, and you don't get that kind of longevity by not meeting customers' needs.
Always remember to get a free trial version of the software and actually try out each piece of software and see if it works for your business. I'm of the opinion that software companies that don't offer a free trial have something to hide--even Baskin & Robbins allows you to taste the ice cream before you buy it. :)
Don't forget to ask your accountant and bookkeeper which software programs they use and recommend. They might be partial to one or the other, and this information might make your decision-making process easier.