In order to help simplify answering the question "What should I observe tonight?", we have consolidated some of the places on the AAVSO website to look for information on urgently-needed observations. As of July 31, 2017, the three webpages:
have been consolidated into one new page:
On this new page, the Alert and Special Notice archives have been combined. By reading the Alert Notices, one can see which stars are in need of observations for observing campaigns or due to discoveries, thus making the Observing Campaigns page unnecessary.
The Alerts/Campaigns list in the AAVSO Target Tool (button at right) shows which stars need observations in which filter(s) in support of a campaign or as follow-up to a discovery; each listing includes a link to the relevant Alert Notice. This list can be sorted by star name, position, filter, etc. 
Special Notices have been discontinued. The type of content that would have been distributed in them is being distributed via Alert Notices and posts to the AAVSO online discussion forums for Campaign & Observation Reports, Time Sensitive Reports, and/or other relevant forums.
Please look around the new page, and also look at the information linked to in the blue box on that page. We hope this consolidation will make it easier for you in planning your observing sessions. Good observing!