You can continue working in US. When you go to Canada the next time, visit US Consulate and get H1B visa stamped in your passport. I presume that your new H1B starts Oct 1 2009. So if you go to Canada now and get H1B stamped, you will be able to re-enter only after Oct 1st.
I would suggest that you get H1B visa stamped after Oct 1st.