to thrive in the forums, you wont get more than 100 - 200$ per design... general pricing goes above 500 - 1500$ per project [including building cms etc]
to get corporate customers you really have to be good. And then just drain their budget as far as you can. I wouldn't start my notepad for less than 400$ if it's for some company that can afford it.
My price can goes from about $150 - about $10,000 However it has nothing to do with who the client is (except I do give discounts to some non-profits). My price is based entirely on (hours it will take) x (hourly rate) + materials (hosting, database etc) Chose a fair hourly rate for your skills and mutiply it by how long it will take.
suggest + 40% on to time you *think* it will take, +20% on total to keep it safe. Then add on $100, and offer it later as a discount if they grumble about price lol - always works
Not bad advise, especially if the project is somewhat new to you. Some of that extra time is generally taken up by discussions with the client, training the client, minor revisions to the site and so on. You don't always have to be the lowest price to still get the bid, in fact most of your better clients will not be accepting the lowest price, they won't trust it. If someone is only going by price, then they are going to be a pain to work with later on.
Drain their budget and they probally wont recommend you. Alot of very successfull designers get alot of business through viral marketing. Find a good medium price, do a good job.