Your invitations are the first impression guests get about your wedding, so take time to get it right. Look at sites selling invitations online and in magazines such as Wedding Ideas as they can provide inspiration. You will soon learn what you do and don't like.
ONLINE PRINTING: There's a pretty wide variety when it comes printing via online companies, so always make sure you can get a proof of your invitation. With some companies, that may cost extra, but it's usually not very much. Much like with at_home printing, your paper options will usually be limited to whatever the company carries, and each company's paper set is going to be slightly different. You can usually request paper samples for free. Here are a few companies I've used with good results: