Contributing to the ‘big picture’ of the world’s wellbeing, and that of the human race in general, is extremely rewarding. That’s probably why so many people are throwing their time and money at huge multinational, supra-national, well-known organizations. While anything anyone does towards achieving a better tomorrow is worthwhile, just like ‘every penny counts’, the most overlooked causes and organizations are the local, grass-roots, or right-around-the-corner organizations. Frequently, this is where your time, money, and effort can go the farthest, and really cause the most impact.
Below is a link about aid effectiveness in local organizations. Although the article is focused mostly on North Africa and the Middle East, the same concept applies in all regions. What many societies need to develop into better conditions is foreign investment, and when working through a highly bureaucracized organization, its more likely that some of the time and money will get lost in the shuffle, and sometimes inefficiencies of said organizations. This is, however, only a small part of the benefits to consider.
Bonus! When were working on a smaller scale, the projects are usually more easily accessible, reducing complications between volunteer/contributor and organization.