Here is a detailed (and informative) overview of pricing schemes for web applications (or Software as a Service as some would like to call them). Includes examples of free, freemium, free trials, pay-as-you-go, and multiple plans.
How to Price your SaaS Application:
The bottom line
Pricing is no rocket science if you rationally arrive at it. Experimenting early on, staying flexible and listening to your customers can really help you nail down the ideal pricing model that works for your business. Allow customers to upgrade/downgrade and even exit without any penalties. Don’t simply underprice for the sake of looking more affordable than your competitor. Keep your conversion and retention ratio in check to back your pricing decision.
[Reproduced from TenMiles's blog]
(Via PluGGd.in.)