Rare? CareerBuilder and HotJobs are consistently rated in the top 5 most popular websites for job searching. This is based on traffic statistics from 2003 onwards.
Craigslist is fast becoming a popular choice for the masses too - more as a first stop for location based job searching online.
If you’re looking for something different, try out
SimplyHired.com - it’s only for the US right now but it’s an impressive job matching service, not just searching. You will need to create a profile and the employers who’ve subscribed to this service will be matched with candidates based on their profiles. It saves a lot of time for both the candidates as well as the employers.
Also, job boards may become a thing of the past as job distribution sites and aggregators become more popular. An example of an aggregator job site is indeed.ca (in Canada).
For Niche job boards, you’ve already mentioned dice.com for tech professionals… also check out healthjobsusa.com and healthcareerweb.com for the Health Care sector.
For jobs in marketing & media, try out talentzoo.com
There are quite a few other Niche Job Boards out there but these are the top ones I could remember off the top of my head.