I manage a website for a non-profit organization. The site will allow people to make donations for the cause. Is purchasing an SSL certificate for this site a good idea? How much will it cost?
It all depends on how you set it up. If you use PayPal and have visitors go to the PayPal website to enter their credit card number, you do not need an SSL certificate. But if you have visitors enter their credit card number directly on your site, you absolutely need an SSL certificate. Certificates can cost from $10 to $1500 dollars depending on the type and who you get them from.
The short answer: NO.
The long answer:
If You are only going to redirect them to some third party site (PayPal or something) to collect donations, there is little need to have a SSL certificate. If You publish a bank account and ask to make a transfer, there is little need too.
You should have a SSL certificate if You ask someone to send important/private (credit cards numbers, addresses, phone numbers) data.
Yes...you should have a certificate for such a site. If you are taking donations directly then you should go for a highly secure certificate. Otherwise, for paypal, you can have a standard certificate, because even paypal recommends to have a ssl installed. The cost will depend upon your need. I got it from rapidsslonline.com. You can check out the same.
Updated answer for 2018
For the most part, every modern website should have an SSL certificate and be using HTTPS for the following reasons:
So there are a lot of good reasons to have an SSL certificate, but "because you take donations" doesn't really factor into the decision. The exception is if you are taking credit cards directly rather than using a third party, in which case you would need to be PCI-DSS compliant and you would probably be reading the compliance documents instead of asking here.
Even though it is a donation site, you must professionally setup the site so that it does not look like a bogus site. Therefore, I still believe you still need to have SSL, regardless of whether you are using PayPal or not.
In case you like to purchase an SSL, you can try http://domreg.asphostserver.com. Please remember that it is far more important to have a professionally secured site, rather than to save $60.00 per year for SSL.
If your not expecting to make much in donations, it maybe worth considering using a 3rd party website (paypal and others) to deal with payment handling. It's free to set up (although they take a small cut of each payment), but you don't have to worry about SSL or any other technical or security administration other than setting it up, which is easy to do.