Yahoo Answers is a peer-to-peer social media question answering service. Users can ask and answer questions and answers are then voted on to rank which one is best. They have warnings all over the site about using it for promotional purposes, but so long as you're actually being helpful you can get by with some promotion. The best part is other search engines index these questions and answers, so you can get on topic incoming links in addition to the direct traffic.
When answering a question, be helpful, include real information, and then you can either include a link to your site in the "Source" area (assuming your website is a source for the information) but also often post questions asking for links to sites, and if your site fits the bill you can just post a link to your site as an answer.
I can usually spend a half hour answering questions and end up with 10 links, and many of my answers will even be voted as "Best."
The thing is though, just with blog & forum participation, you do not want to force it. If you cannot find a question that your site's content can answer, don't fudge it and post a link on an only slightly related question, instead just try again tomorrow.
Another thing you can do, which is decidedly gray hat but is hard to catch, would be to do an exchange with a friend. Have a friend post a question tailored to your site, and you provide the answer. Then you post a question tailored to his site, and he can answer. Or, if your site is a true authority for a topic, you can simply post a question tailored so well that a user you don't even know could end up posting a link. You should still follow all my other advice about making it look genuine and posting real helpful information of course.
A press release is a short informative notice sent to members of the press about your business or a new product or service you are offering. Services like PRWeb have made it very easy to create such a press release, vastly lowering the barrier of entry to this type of promotion for small businesses.
You shouldn't have any dreams of being contacted by all these media sources for interviews after sending out your press release. That is a long shot, most press releases are ignored simply because there are so many sent out on a daily basis.
However, there is always the slim shot that you could hit just the right nerve with an editor to get a media mention. This can be easier if you live in a small or rural area. Knowing of an Internet business in their local area can give small rural newspapers or other news outlets a go-to-guy for Internet related news stories. You could also peek their interest for one of those fluff pieces about successful entrepreneurs.
However, when you release a press release through PRWeb it will always gain you incoming links because PRWeb itself will list the release in their directory and places they syndicate to will as well. It may not be a huge amount of incoming links, but they will be incoming links.
So, when doing a press release, its okay to hope for some media mentions, but realistically you should only expect the link from one or two places just listing the press release.