Adobe Illustrator is the standard software when it comes to vector image editing.
This video is amazing.
Smashing Manazine has a post with many illustrations that were created using Illustrator.
Price:
You can buy Illustrator for $599. Another option is to aquire it throught the Creative Cloud, which you can get all the software for $49.99 per month or just get Illustrator for $19.99 per month.
Tutorials:
Know a good Illustrator resource? Send us a message!