Reinventing the wheel doesn't make sense. Neither does creating SMART Board lessons from scratch. Chances are someone out there has a lesson built just for you on your desired topic or field of study. Of course, it might not be perfect, but you can always tweak them to your liking.
Check out SMART Exchange, which is probably one of the best (and largest) collection of lessons designed for the SMART Board. In fact, as of November 2010 there were over 19,000 lessons available to download plus an additional 10,000 other downloadable resources. Lessons can be searched by subject, grade and content standard. This resource, maintained by SMART Technologies, is growing all the time.
You can even look up Ohio Academic Content Standards for grades K-12 and view resources directly from the content standards listed on their site. Could it get any easier than that? While these resources can help you as the teacher save time preparing for your lessons, ultimately it's just another tool to help our students learn.