These are recommended plugins. If you find a better one let me know.
Drawing - Hands down it's Gliffy.
Evaluating
Encryption
Looks promising, no public key, but simple enough - https://marketplace.atlassian.com/plugins/com.prcpo.confluence.plugins.secure-content-block
Form Capture
http://confluence.atlassian.com/display/CONFHOST/Capturing+data+with+forms - seems to have a good run down of the available options.
http://blogs.atlassian.com/2009/05/confluence_wufo/ - expensive but looks to be very powerful and mature. Video demo on home page. Requires an additional server.
Workflow
Still looking, have not tried anything yet.