This afternoon I received an email from a reader who wondered what happened to Wiki Summarize. I don't know other than it is no longer online. It was a nice tool that helped students see long Wikipedia entries in chunks. It also included a web of related terms to help students see how topics were connected. While I haven't found anything that is exactly like Wiki Summarizer, I do have a few alternatives to suggest trying.
SummarizeThis is a free tool that summarizes the main point(s) of long articles that you find on the web. To use SummarizeThis you just copy and paste text into the summary box and click "summarize." A summary of the text then appears above the original text that you copied.
instaGrok can be used by students to read summaries of topics that they are researching. You can use instaGrok to search a topic and quickly get lists of facts on that topic, links to information on that topic, videos, images, and quizzes on the topic. If you want to refine or alter your search, just click on another term in the web of search terms. instaGrok offers some bookmarking tools and tools for creating journals of notes.
Wolfram Alpha offers a free Google Docs Add-on that students can use to conduct research without leaving the documents they're viewing. Wolfram Alpha can help students quickly locate information about famous people in history, locate socioeconomic data, find science data, and even help students find information about music theory. Unlike on Google or Bing, when students search on Wolfram Alpha they won't be shown a list of links. When students search Wolfram Alpha they will be shown organized collections of information. In the video embedded below I demonstrate how to install and use the Wolfram Alpha Google Docs Add-on.