Absolutely no. While on an H1B you can only work for the employer who sponsored you for the visa. You can volunteer at a church or charitable organization but you cannot legally take paid employment. The H1 visa is a special category that has been created to import labor from overseas for jobs for which no US citizens or permanent residents can be found (at least in theory, though, it seems the loopholes are being exploited all the time). Taking even a part time job will be considered as breaking the law.