I'd very interested in using Uber, and I'd like to have a look at what they have to offer in terms of available car sizes, rates, etc., but I can't work out how to do so without signing up which requires my credit card details. I have no intention of giving out those details without being to see what I might be paying for first, so surely there is a way of getting ride quotes without having to do so, as per accommodation and service-offering websites. Just can't seem to find it...
Simple: use a third-party site like Uber Estimate. Obviously any results you'll get from here will be unofficial and not guaranteed, but they seem to be pulling data directly from the app.
Note that even in the Uber app itself, you don't have precise control over what you'll get: for most cities, your choices are basically "normal cars driven by random people" (UberX) and "luxury cars driven by pros" (UberBlack). But it's not going to let you pick between a Ford Taurus and a Toyota Corolla.
Uber.com provides an official Fare Estimator now, which gives out a range for all types of transport.