The steady growth of the World Wide Web raises challenges regarding the preservation of meaningful Web data. Tools used currently by Web archivists blindly crawl and store Web pages found while crawling, disregarding the kind of Web site currently accessed (which leads to suboptimal crawling strategies) and whatever structured content is contained in Web pages (which results in page-level archives whose content is hard to exploit). We focus in this PhD work on the crawling and archiving of publicly accessible Web applications, especially those of the social Web. A Web application is any application that uses Web standards such as HTML and HTTP to publish information on the Web, accessible by Web browsers. Examples include Web forums, social networks, geolocation services, etc. We claim that the best strategy to crawl these applications is to make the Web crawler aware of the kind of application currently processed, allowing it to refine the list of URLs to process, and to annotate the archive with information about the structure of crawled content. We add adaptive characteristics to an archival Web crawler: being able to identify when a Web page belongs to a given Web application and applying the appropriate crawling and content extraction methodology.