For almost all business Quickbooks Simple Start, Quickbooks Pro 2007, or Quickbooks Online edition will be all you will ever need.  Quickbooks Premier, Quickbooks Enterprise, Quickbooks POS will be overkill for most businesses.   To decide what Quickbooks version you need you can paste this link for a comprehensive comparison....http://quickbooks.intuit.com/product/accounting_software/product_comparison.jhtml?priority=Low 

Here are some movies that will really help in understanding the basics of the Quickbooks line, please copy and paste the links.

Quickbooks Free Edition and Simple start -http://http-download.intuit.com/http.intuit/CMO/quickbooks/lava/movies/71-cor-o1.html

Quickbooks Pro -http://http-download.intuit.com/http.intuit/CMO/quickbooks/lava/movies/71-cor-o2.html

Quickbooks Online -http://oe.quickbooks.com/see_producttour2.cfm

Quickbooks Premeir Edition -http://http-download.intuit.com/http.intuit/CMO/quickbooks/lava/movies/71-cor-o3.html

Quickbooks Enterprise 7.0 -http://http-download.intuit.com/http.intuit/CMO/quickbooks/lava/movies/71-eps-o1.html

Quickbooks Point of Sale 6.0 -http://http-download.intuit.com/http.intuit/CMO/quickbooks/lava/movies/61-pos-o1.html

Quickbooks makes it extremely easy to print checks, pay bills, track expenses, payroll, and create invoices.   Simple Start, Pro and the online edition do those things with ease and it is usually the need for one of the mentioned tasks that push people the quickbooks direction.  By far the most popular software is Quickbooks Pro 2007.  In fact it is sold more than any other software on Amazon.com...even more than Microsoft products.  One new feature in Quickbooks Pro 2007 is the ability to take credit cards inside the Quickbooks software.  Here is a movie with a demonstration....http://www.quickbooksmerchantservice.com/flash/qbms_demo/lesson_1.html

Quickbooks Merchant Services will also give you a free copy of Quickbooks Pro 2007 by signing up for a merchant account.  To receive your free retail copy of Quickbooks Pro 2008 and a free USB swiper valued at $199 call Quickbooks merchant services at 1-800-539-2141