+1 for Solidworks.
If you're not sure what software to use, just get a couple of them and try them out.
I personally like Solidworks because it is what I use at work and I have found it extremely intuitive compared to NX.
I also like Solidworks because the process to get it is really straight forward.
You click the apply for team sponsorship link on
this page , fill out the form, and they e-mail you download instructions within a couple days (2 days when our team did it). A really useful thing for us was that the software was licensed for team's personal computers, not for school computers. So we were able to give our students and mentors licenses to put on their personal computers.