Any thoughts on how to get LaTeX in OneNote?
[Not quite the answer you are expecting]
No, there's no way to include LaTeX (and I assume you mean the mathematics typeset with it) in OneNote.
One workaround that is sort-of-kinda-working (with severe caveats), so go ahead, if you absolutely need to. This applies to OneNote 2007, so if you have more recent version, it could be somewhat different.
Now, the caveats:
That being said, if you'd like to have a note-taking application together with LaTeX mathematics, I suggest turning to a wiki software that supports advanced typeset mathematics. I personally use Confluence, but free alternatives are available (the example that first comes to mind is MediaWiki, which powers Wikipedia, and it has comprehensive LaTeX support).
You will need to set up and administer a web server (and most likely a database server as well) in order to use wiki software, but in the long term, and especially if you are serious about having a space to collect your stuff, this is a superior solution.
then type your equation and hit the Enter key. Right click on the automatically generated image and copy it into my OneNote file.