D-mon Connect is a program to visually design NFAs and DFAs, and you will be able to convert between the two. You will also be able to convert to or from a regular expression. This program is written in JAVA, but it is using SWT for the interface instead of Swing. It should work on all platforms that have a version of eclipse. You will also be able to check strings against the NFA/DFA that you create.
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Screen shot of the interface