Starting from January 1, 2015 all new funding agreements with the Bill and Melinda Gates Foundation will be under the terms of its new open access policy, which requires all the research output to be discoverable and accessible on-line, under the Creative Commons Attribution 4.0 Generic License (CC BY 4.0) or an equivalent license, immediately upon publication, with no embargo period. The very same policy states that the foundation will pay reasonable fees required by a publisher to effect publication on these terms. That means that all Article Processing Charges required by publishers for immediate open access will be covered by the Foundation.
Moreover, the data underlying the published research results has to be immediately accessible and open. This seems to be quite a radical policy as some grant programs funded by the Foundation may deal with medical records and personal data, and at this time the policy do not allow any exceptions, which is quite unusual for open data policies. The contradiction between openness and privacy is a subject of broad discussion within the research community and it would be good to see funders participating in this discussion in a less assertive way (in my opinion, the approach to open data policy represented by the Horizon 2020 is much more reasonable).
Although the Bill and Milanda Gates Foundation offers grants mostly to non governmental organizations, at this moment there is several interesting calls open to individual researchers dealing with applied sciences. The grants are offered mostly to those working in low and middle income countries (although international partnerships are welcome). For current calls that might be of your interest look here and here. New grant opportunities will probably appear on this website.