wikia.com have a CYOA database with a bunch of editable IF games which
can be played and/or improved online:

http://cyoa.wikia.com/wiki/CYOA_Database

Example (created by Example)
Benign (created by Squeegy)
Salsa Kingdom Seige (created by Revenant Jesus)
Haunted Horrors Series (created by Squeegy)
The Adventure of Squeegy (created by Unknown)
Origin (created by Gooseheaded)
Phone Booth (created by Eddward)
A Most Squamous Adventure (created by Fwoop)
Survival in the City (created by Pitchblack)
The Lewis Gram Case (created by Carlos Cano)
Nuclear Rush (created by Holygiant)

I will look into some of them and probably write one or more reviews
when I'm done with my own work.

Greets,
Emilian K.