I just found a new answer to this question (and actually i find it the best one in some cases):
You can use podio.com which is a free (up to 5 members in one organisation) ERP
(Enterprise resource planning (ERP) systems integrate internal and external management information across an entire organization. (via wikipedia)), that allows creation of fully customizable webform, that can be added anywhere you wish. What's more, the input that your webform gathers can be easily managed: for example added into you contact list, added to tasks so you can check wether you or someone from your team handled enquiries. More on that here: http://blog.podio.com/2012/08/07/styleyourwebform/
some pros:
- can be added anywhere you wish (you just have to specify subdomains its going to be used on)
- you can customize form in minutes
- you can add captcha (or some other spam protection) with one click
- you can easily manage webform leads
cons:
- youd have to create a podio acc for every client you want to set up webform for in order to avoid sharing confidential info
