Finstocks Prices and Graphs of Finnish stocks. Provided by the University of Vaasa. Also has a nice search feature. If you search for a company, you may also get some articles about the company, and this site looks like a nice site for researching the larger Finnish companies. Data include address, phone, fax, CEO, sales, exports, and sector.
Some companies also have their logo and a description.
This link is essentially a search from the above site. The search features are available in Finnish and English, but when you get a list of firms, it's all in Finnish. Most of the time, you get the address, and sometimes you get an advertisement which looks as if it were scanned from the actual yellow pages. These ads are, of course, in Finnish. Has a directory of over 100 Finnish electrotechnical companies.