(I feel that I have asked so much of this forum that it is good that I have a question I can give something back to. I may be (relatively) new to web work, but have long term experience in another aspect of design.
I can suggest that fees needn't be an either/or situation (fixed or timecharge).
I have worked with a combination of many - if there is work either you or the client can be specific about, and you are confident that you can do it in a certain amount of time, it is worth working out a fixed figure. The client then has reassurance and can budget and predict costs with some certainty. You have the confidence as well, that you will get paid for the time you've put in.
If there is a chance that either the work cannot be closely predicted at quote stage and there may be more to it than meets the eye, or you think there may be other pieces of work they may add along the way that haven't been specified at brief stage, then state in your quote that such work would be subject to a timecharge rate per hour or day. You could add that such things may take x number of hours and this allows the client to work out for themselves what something may cost overall, once they add up the fixed figure with what they think might be on a timecharge basis.
In terms of what you charge, you could get back to basics and work out how many hours a week you're willing to put in, and how much you would like to earn per week, and see if that gets you an hourly rate. Have in mind the costs of your taxes, materials, expenses and insurances that you need to cover as well as the champagne and truffles you need to survive.
I know of some that knowingly and admittedly charge hourly rates much more than others, but they have an established reputation of actually cracking on with the work so clients take confidence that they may pay less overall, because its taken that designer less time.
Also think about how much a project will mean to your experience, your portfolio, and your reputation, as this may have a bearing on how much you are willing to do the work for. Don't get yourself into difficulty by 'buying' the job and then find your client isn't happy with an increase in rates when it comes to subsequent work.
Some people I know work out what they think the client will pay, or more importantly what they won't pay, and they will price a job on that basis.
My motto is be honest. I would rather a client came back with more work, and made referrals, than I made a killin on each one and never built a working relationship. Hope some of this helps.
