In my years of doing freelance works — web designing, programming, post production, technical tutorials and consulting — I learned that the best way to price the services was computing it by the hour while pegging a minimum limit.
Thus, if you are to design a website or do some programming, estimate how long it will take you to finish the job then multiply it with your standard hourly rate. Take the total and add or subtract at most 20% from it depending on the type of client you have — 20% more for corporate clients and 20% less if personal clients. I made the 20% offset because corporate clients tend to ask more personal meetings and beta presentations. In the same sense, any additional revisions to the project allows for incremental fees.
It becomes even much easier if you do technical tutorials or on-site consulting. Rates for speaking engagements may also follow the same scheme but you need to round it off to either half day or whole day engagements, half day taking 4 hours and whole day at 8 hours.