Any thoughts on if/how I can use someone else's blog for adding a link to my site?

For example, I found a very "niche-y" blog that has very relavant content related to my site. Can I post a comment that includes the URL of my site?

Thanks for your help. I don't want to "spam" someone's blog... :o

I dont see any thing wrong if your intention is not to spam ... If adding the URL is an added value for the user visiting the blog then its good ... I am not sure if it will help in ranking but it might get you some traffic to your site ...

maybe that's not too much help since many people don't click on comment links because they think it's spam, but instead you can post asking the blog owner to evaluate your link (if he/she wants to) and after he/she will put a link to your website and it's readers will trust it

Great suggestions. Thanks! :)