For Div 1: Official visits are allowed beginning opening day of classes your senior year. You may make only one official visit per college and up to a maximum of five official visits to Div 1 colleges.
For Div 2: You may make official visits starting Jan 1 of your junior year. You may make only one official visit per college, however, there is no limit to the number of colleges you can do an official visit.
I wanted to add a reminder for anyone who's planning on playing D1 or D2 softball. Don't forget to register with the NCAA Eligibility Center. Here is the link: Future | NCAA.org - The Official Site of the NCAA Registration is NOT required for D3 sports.
There's a link titled 'Student-Athlete Registration' on the right side of the page. I can't remember how much it cost, but I think it was about $35?
It is $75 now. This is a good post. This applies to JUCO athletes also. My DD was asked about transferring to a D2 school a couple of weeks ago. She never went through the NCAA since she was originally going NAIA then switched to a JUCO for financial reasons. Since she never registered with the NCAA eligibility center there is no way the NCAA will qualify her to play NCAA ball in the 3 weeks she has left before she reports to her JUCO. So it looks like she missed that opportunity.