Hypnotism can be a great means of unlocking your inner girl's potential...or just an immersive form of erotica.
We've already covered subviewer, but there are many other types of hypnosis-related stuff. I've also mentioned Anna Malice's Sissy Self Hypnosis - which has daily sissy hypnosis videos from various places on the web (as well as regular porn and fetish videos).
Warp My Mind has an extensive collection of hypnosis files - along with inductions and other hypnosis-related things. The file browser has categories that cover a variety of stuff, but since you're at Natalienne's Sissy Spot I would guess the Feminization files would be the most appealing. The site requires registration, but with that registration you can download all the free files you want.
I'll recommend the Little Miss Squidgy or one of its continuations. Can you pass her test, sissy?
If you'd like something with a more human voice (although the text-to-speech in the LMS files is intentional and doesn't sound too bad) I would recommend Elena McIvor's cock conversion mantra to go with the actual file (hidden away on a different site).
Allison In Love doesn't seem to be active any more, but her files (which are less sexual in nature) are also available.