I don’t make cakes as my business, but I do know the web and other types of freelancing.
Word of mouth is great of course, but you often want to have something to give them too. This means fliers, business cards, or other ideas people have already pointed out, like brochures.
Having a web presence works hand in hand with this, just put your website URL on your fliers or cards. You can have your whole cake portfolio on your site with pricing or ordering information, make a Facebook page to go along with it and add a ‘like’ button so people can share it around, and maybe get your site listed in some local directories.
If you have any questions about websites or the online advertising side of things, I don’t mind answering them if I can be of help.