A lot depends on the size of the plot.
Small plots (around 1/2 acre), about the best you can do is a fall planting of a mix of wheat, oats and Ladino clover. The clover will just barely get started in the fall/winter, but will explode in the spring and last until around May/June before going dormant - longer if you get a wet summer. If the wheat/oats start to get tall in the spring you need to cut it back to release the clover. Planting white clover in the spring is a hit or miss proposition - usually a miss. It needs to get established in the fall. Crimson clover usually does OK with a spring planting.
For large plots of an acre or more Iron/Clay peas are hard to beat.