sure, what you would want to do is create a text file on your server (with writeable permissions). Create a form with the fields you want. When they fill out that form, you open the file for writing (use 'w' for your mode if you want newest comments uptop. see fopen()), write to it, then close it.
You'll need
fopen()
fwrite()
fclose()
Then when you want to display the comments, just open up the textfile and display it. When you fopen() this time, use 'r' as your mode. Open the file, display it on your page, then use fclose()
Check out the links above. There are a ton of user-submitted code/comments for this.
Cgraz