Go look for yourself there are hundreds if not thousands of them. But then again, it depends on how you define commercial- Does the site have to sell something, or if the site earns money from advertising, is it commercial?
There are many sites that actively promote their companies but the biggest one is WikiTravel that has thousands of links on Wikipedia and was just bought by internet brands. What do expect they will do with Wikitravel.. There is defintely some probelms over at wiki and their method of saying who can have an external link. Smells like DMOZ.
Check your serach terms in Google after acouple of days. It will show wikipedia above you! If you can live with that its o.k. Put your link on a page under the following conditions: (01) You have meaningfully contributed to the page. (02) Your site would add value to that page in ...that it will offer more information on the subject. Please do not spam it! I have great respect for the guys that started it.
That in my books is tops, if it is going to rank above you... any site that does that is higher on the list of most desirable domains / pages to get a link from.
I think Google may assign a no-follow to Wikipedia becaus ethey know people are using it to link to their sites for PR and traffic. THis may hurt the credability of Wikipedia. If on the other hand, there is no PR to be had, people won't abuse it.