I am new in sequencing and in my research group they always have used Bioedit, but it doesn't work on Mac... I wonder if is there any similar program that can be used in Mac without using Parallel. Thanks
AliView is the best there is for OSX right now. http://www.ormbunkar.se/aliview/
It works differently than BioEdit as far as selecting blocks and moving them and all, but once you get the hang of it it is very good. JalView and others work too, but AliView and BioEdit are far superior. I have run BioEdit on Macs, both by using WINE and by installing a full Windows OS under VMWare virtual machine, but neither of those solutions is very good on a MacBook.
AliView is quite fast and good as Brian suggested, BioEdit is good. But personaly I would recommend Jalview, it's fast and multiplatform, it works anywhere you have java (which is everywhere). You can grab it here: http://www.jalview.org it comes with some pretty nifty features also such as the applet. You can also take a look at Jemboss: http://emboss.sourceforge.net/Jemboss/jae.html
Free Mac Software for Molecular Biologists - Bitesize Bio gives 10 links is great piece of software from NCBI is a sequence viewer verified, hope help you.
Geneious software is very helpful. You can do almost everything with its free version or pay to perform more advanced study. I used it for my PhD data analysis. Also Sequencher is very famous, but I think you have to pay for the licence.