Finding a QR code generator is actually quite a bit easier than you might have expected. Like bar codes, QR codes are capable of storing a specific amount of data, and each black block on the white grid tells the QR code reader a specific thing. This means that regardless of what QR code generator you use, it'll always end up pointing to that specific URL.
However, it should be noted that if you use a URL shortener for simplicity's sake – which is a good idea – you should make sure that you use one which has non-expiring short URLs, or at least URLs that are guaranteed to stay up for at least five years. This is especially crucial if they are going to be on product packaging, in art designs, or on business cards. This will make sure that people can scan the codes for a reasonable amount of time, and prevents you from spending more money and time on reprints in the case of the short URL expiring!
In addition to those tips, make sure you pick a QR code generator that generates a big enough image that you can scale it up or down as needed. After all, if you plan on creating a large project, such as a design on a poster, billboard, or even the side of a bus, you're going to want to be able to see the detail of the code to reproduce it accurately.