http://www.dol.gov/wecanhelp/h1bworkers.htm
We regularly hear from candidate's telling us that their H1 employer is requiring certain things from them as it relates to immigration costs and work duration bonds (among other things). The percentage of candidate's who are not informed about their working rights in the US is alerting, especially when they are public knowledge and easily searchable. 
Here are a few important points, please navigate to the DOL link for further information:
" Your employer may not require you to pay, either directly or indirectly, any part of the petition filing fee; or to pay a financial penalty for leaving employment before a date set in the employment contract"
"Your H-1B employer may not intimidate, threaten, blacklist, discharge, or in any other manner discriminate against any employee, former employee, or job applicant for disclosing information...