There are scores of online marketing techniques that are effective in building relationships that can lead to links to your site, but there is no reason to stop there. Do the major influencers in your space speak at conferences? Then go to it, and introduce yourself. This can include not only bloggers, but other people influential in your space.
Another related tactic is consider contacting the publisher of an authoritative site and offer them a free seminar/webinar, with you as the speaker. Call it part of your company’s outreach campaign to build relationships with leaders in the space.
If you do this, make sure you articulate well the unique nature of what you will present. You have to attract their interest with the pitch before you can take the next step. Then, make sure you bring a lot of value in the actual presentation itself.
Then collect business cards, answer questions, and make yourself available to answer questions after the presentation by phone or email. Once you have done that you will have a ton of relationships with people involved in the authoritative site.
There are other ways to extend this too. For example, you can sponsor an organization in some fashion. There are, of course, sites that link to their sponsors, and this may be a win, but it is a link that Google will want to discount (because it is effectively purchased) so you should not count on that aspect of it. The other win is that sponsors often are able to establish a deeper relationship with the organizations that they sponsor.
Last, but not least, most likely you have other businesses/organizations that you interact with in the normal course of your business. Once again, you can ask them directly for links, but you can also ask them for introductions to other people in your space. This type of networking can be quite an effective way to build relationships that eventually lead to high value links.
You don’t want to expend this level of effort for garden variety links, but for high quality links it can come with a huge ROI.