TwitHire is a simple listing of job announcements in reverse chronological order, with links to the announcements online. It has separate tabs for design and computer programming jobs. The listings give the job's geographic location with varying specificity, from names of cities to "north of the Equator". There's no charge to employers for posting job announcements.
TwitterJobSearch aggregates job announcements posted on Twitter, and lets visitors search its collection or browse through categories, with links going to the online announcements. Searching on the term "science" returned some 16,000 results. A more targeted search using the term "Toxicology" returned 53 entries. Another targeted search, "materials science California", provided 62 results. Signing in with your Twitter account can let you save or retweet (forward) the announcements.
TweetMyJobs operates more like a job board using Twitter as its engine. Job seekers create an account, enter their employment criteria and preferences, and receive Twitter messages when jobs are posted in TweetMyJobs match these factors. The service charges employers for posting their announcements: $0.99 for one day to $9.99 for 30 days.
Career Hub reminds Twittering job seekers that recruiters and hiring managers also use Twitter, thus it pays keeping your tweets in good taste. And, of course, you can follow Science Careers on Twitter.