One of the things that I like about the internet is that amongst the commerce, the blogs, news, corporate and organizational sites on the web are sites where just by clicking a link, you can give tzedakah (a Hebrew word meaning righteouness, the word we use instead of charity) while online. Of course, there are many sites where you can use a credit card and give money to a favorite recipient, but what I am speaking of are sites where you can contribute to others for free without having to do anything more than just click.
There are many such sites for many many causes. Some people have made lists of the sites. For example:
Click to Cure Cancer (See the list at the bottom of the page.)
Help Others for Free (Listed by catagory.)
Care 2 Click to Donate
Go and give tzedakah!
Amelah's Blog (Thoughts from a Rabbi) 