How can a researcher from a third-world country publish or otherwise disseminate an interesting result?
I guess that no one is going to invite you from overseas for a seminar unless they know you already. One of the best ways to disseminate your research is conference participation, but coming from a third-world country puts you at a disadvantage in terms of funding and travel possibilities. Sometimes conferences have travel grants for students and early career researchers (I don't know if you fit inside this category), which you can apply for. This can offset some of the costs (but not all, unfortunately). Watch out for this kind of opportunities.

Another thing that you should do is writing down your results in a preprint and trying to get it published. Once you have a preprint, you can send it to a (small) number of researchers working on the same area to try and get them interested. This could be a subset of the people you cite, for instance. Watch out for signs of feedback (positive and negative) from their part and don't overdo it -- you don't want to be considered a spammer.