We bought ours at Michaels in the US. Walmart sells some to make at home.
We did ours with cardsandpockets.com. Was all pre-cut and we just designed the invites as we liked. We also added some heat embossing, which made them look professional and added a personal touch to the design. Here is a good tutorial: http://www.weddingbee.com/2009/01/14/heat-embossing/
You can get embossing supplies at any craft/scrapbook shop. I would recommend Bonnidée in Point Claire (http://www.bonnidee.com/en/). They were very helpful and gave me a on the spot demo when I stopped in on how to emboss. They also have some good samples and ideas for wedding invites and am sure they do workshops.
I haven't used them, but you might be interested to know that Bureau en Gros stocks card paper with wedding-themed designs. You can print on them directly using your home printer.
I still remember the time I had to go arrange my brother's wedding and I had to go to the wedding planner to plan all of the things out from the venue, food, floral arrangement, and God know what else. Hence for a month, the Assignment Help Services In Edinburgh were handling all my academic-related tasks because I was handling most of the wedding arrangements.
Click on each tool to see a sample.