I recently wanted to add a contact form to a sidebar in wordpress as quicly as possible and I think the solution I found was great, so here you go.

First install this great Wordpress contact form. Then create a new text widget and add your text/html and then [contact-form].

One gotcha, I came across is that Wordpress didn’t parse the short codes, but thanks to this thread about short codes broken in text widgets, I just added:

add_filter('widget_text', 'do_shortcode'); 

I just added...to the functions.php file and was in business.