This has to be one of the most popular questions business owners ask their accountants, purely looking at it from a financial perspective I would recommend trying out these free calculators:

http://listentotaxman.com/index.php

This allows you to calculate the Tax and NI payable on Salaries

http://www.contractorcalculator.co.uk/Dividend_Tax_Summary.aspx?uid=0&logon=False&psalary=50000&div=1&status=OutsideIR35&pyt=LimitedCompany&expenses=3000&other=0&pension=0&tc=747L&age=30&salary=12000&rate=25&rt=Hourly&rt2=Hourly&weeks=44&dwpw=5&dwpw2=5&hours=37.5&dni=3000&tty=2011&rate2=25&weeks2=44&hours2=37.5&status2=OutsideIR35&psalary2=50000&mir=0.05&ma=200000&mp=25&cid=0&vat=1&vi=False&cby=1&ar=1&gs1=0&gs2=0&gs3=0&gs4=0&nd=80000&pbt=1&dpo=16-Jul-2011&dop=01-Jan-0001&inv=1&hpd=11&me=150&vt=Car&mpw=0&mpc=0&pt=Monthly&ace=500&mt=Parasol&wl=InsideLondon&uds=Basic&Host=LOCAL

This link calculates the tax on dividends (Dividends are paid after the company has paid Corporation Tax which is 21% for small companies)

steve@bicknells.net