There is a simple script called Form Mail (http://www.scriptarchive.com/formmail.html
There is an option for a paid service, but they also have a free download of the script you can install on your own site. I've used it in the past and it was pretty easy to use.
Also, this may or may not help you, but I work with WordPress sites a lot and there is a great plugin called Gravity Forms (has to be purchased). It has some really nice functionality. I don't know what type of projects you're working on exactly and whether it would make sense to install WordPress for them, but if so, that plugin is the best I've found.