How do I float a sidebar inside the main body?

I'm trying to figure out the best way to float a sidebar inside the main body of my page (not the full height of the main body, just a section in the middle). I'm new to CSS, but I'm thinking I could define a style for a sidebar using margins, but then I'm not sure how this would work inside the main body (would they overlap?). I tried to span a regular ol' table, but the main body text wouldn't display beside it.

Thanks in advance!

You'd just want to make sure that the sidebar was inside of the main div, and float it right:

<div id="main-content">
<div id="sidebar">
... sidebar stuffs ...
</div>
... main stuffs ...
</div>

EDIT: If you just want it floating to the right of a specific section of your main text (which as I reread your post might of been what you were asking about) just enclose that section in a div:

<div id="main-content">
.. main stuff ..
<div>
.. more main stuff
<div id="sidebar">
.. sidebar ..
</div>
</div>
.. more main stuff ..
</div>