TextSpline is a deceptively simple-looking screensaver that animates a line of text (in your choice of font and color) traveling over a randomly generated curvy line (with optional loops).
Uses Core Animation code that should be compatible with Mac OS 10.5 and later.
Note that the saver doesn't limit the length of the line of text, however since each letter uses up some resources, I would advise against using a text line greater than 128 characters in length (plus, it's hard to read long text while it's animating anyway).
Spacing between characters was tricky to do, and depending on the current CPU load on your system, you might find the characters get a little jammed together. Also, some fonts (e.g. Zapfino) might get cut off, due to glyph bounds complexity. I may try to expose a user setting to having better control of spacing between characters in a future version.