I did a few jobs as a freelancer on elance.com and made just over $800US. How do I include this in my income taxes? Casual income? How do I tackle US$ to CAD$ conversion?

You are able to claim this as casual income.  Whether you claim it as self employment or casual, the tax hit is the same.

As to converting to CDN funds, you would take each payment you received, use the Bank of Canada website to look up the conversion rate for each date, and calculate accordingly.

Thank you. This helps a lot. Elance also charges an 8.75% fee for each payment. Can I claim that as an employment expense? TurboTax states that "Canada Revenue Agency (CRA) requires that your employer complete and sign Form T2200 in order for you to be eligible to claim most employment expenses. You do not have to submit this form with your return; however, keep it in case CRA asks to see it." Do I have to fill this form out given that my "employer" is a website (Elance)? I don't think I'd ever be able to get this signed by anyone.

The T2200 form applies to employment income...in your case, it's either casual labour and/or self employment.  If you were claiming the income as self employment you would include it as an expense on the self employment form of the tax return (T2125).  For the amounts you are claiming as income, just claim casual...deduct the expense from the gross, and claim the balance as casual income.  Just keep the documentation yourself to support where you get the amount claimed.

That's simple enough. Thank you so much! This has been very helpful.