BlueLake
Piran is correct re issues with validity period of cacert certificates.
If you can locate a "real person" in your area and physically meet up with them, then you can have a cacert certificate issued for 2 years rather than 6 months (the default "effort free" validity period). Visitors to your website still need to install the CACERT root certificate available from the cacert website. So you could say there is still some effort required to get trust when using free cacert certificates. Trust has a price. Read more about it on the cacert website.
Certificate authorities need to pay tens of thousands of dollars to the browser publishers to be included in the root certificate. Cacert is the organisation currently attempting to achieve what you are asking for.
There are a number of lower cost commercial certificate offerings around that I believe are trusted by browsers (eg the Microsoft issued default root certificates installed in browsers).
Search Google for cheap offerings, take a look at GoDaddy.
Note that the root certificate issued by Microsoft & others needs to be updated every few years (which happens automatically with a browser update). There is a cost to browser publishers to maintain & update root certificates, so I guess it's reasonable to expect there to be a cost to the end user.
I think you can get an acceptable certificate for a few hundred dollars per year rather than paying thousands of dollars for a "big name" certificate. Most small businesses could afford the lesser amount, it's in effect a necessary cost to do secure online business.