One thing I need to do periodically at work is to monitor for web page changes. By periodically, I mean once or twice a year, just long enough for me to forget completely. For some reason, it seems wrong to depend on my work laptop to do this; I wanted a web service.
The one that should never have been on my list was PageHammer. The site takes forever to load, and it would never let me register. I liked the teaser feature of customizable intervals, but it's got to work ya know. Bah humbug.
I tried FollowThatPage; it works, but I wish I could change the interval. Weekly is often enough for many things I check online. I like the keyword matching (or excluding) feature so I can pinpoint the interesting changes. The batch upload and Firefox extension are useful bonus features. The Firefox extension swayed me, as it looks like the developers are active, and interested in ease of use.
The other promising one was ChangeDetect. This service also supports bulk import, also filters for regexp and negative regexp, and could even throttle back to monthly checks. However, I'm leery of services that have a paid tier when I have exactly one web page in this "must check once or twice a year" category. (It's not worth much money to me when I can put a reminder on my calendar for the low-tech route.)
I think ChangeDetection.com would also work, but it doesn't lure me in promising some of the features that caught my eye from the other services.