The National Conference of State Legislatures has authored two useful reference charts.

Here is a chart that shows the partisan composition of each state’s legislative chambers. This data is very tough to track, because it changes constantly, due to resignations, deaths, and replacement actions, including special elections, or in some states appointments.

Here is a chart that shows when each state’s legislature convenes this year. Over half of them are already sitting. Thanks to Thomas Jones for both links.