Also, I've highlighted ones here that need to be given some credit because they provide tools for workflow developers or are great examples of how to develop.
phyllisstein should get some cred for his python library: http://www.alfredforum.com/topic/403-alp-a-python-workflow-module/
robhor should get some for showing us how to do drill-down menus: http://www.alfredforum.com/topic/376-drill-down-menus-movie-search-omdb-api-alfred-repo/ (useful for people making more advanced workflows).
tomhunt needs cred for the initial alfpt (http://www.alfredforum.com/topic/234-alfpt-alfred-package-tools-workflow-installerupdater/)
and, by extension, Olivier needs cred for the upcoming package manager (http://www.alfredforum.com/topic/829-apm-alfred-package-manager-need-testers/)
EggTimer from CarlosNZ — I don't use the EggTimer, but it needs to be highlighted as to how a very complex workflow could be made. (http://www.alfredforum.com/topic/275-eggtimer-v2-updated-to-beta4d/)
I'm partial to my Caffeinate Script (http://www.alfredforum.com/topic/710-toggle-caffeine/#entry3419), but any of the Caffeine ones on there could work.