Here are several lists of software products built in Delphi:
Embarcadero has gathered a list of mostly-high-profile applications, and published it here. There are 172 entries as of Nov. 2010. Some of the products there have screenshots and case studies available, if you follow the links to the product makers' sites.
Over on the Delphi Wikia, there is a list of Delphi applications. It is unclear how many are on that list. By the way, there is an RSS available to track updates to that site, but the links to it are incorrect. The valid feed link is here
This list was published for years at http://www.balticsolutions.com/bwd/ but that site has been down since 2007. In 2010, Kyle Cordes had a web-scraping person retrieve a portion of it (as much as could be found) from web.archive.org. Then the products and web sites were briefly checked, and all of the no-longer-working entries removed. The results are published here. Because the data is an ordinary HTML table, you can use your browser's Find feature to search the list; you can also view the data full-page here.
This list captures a broad swatch of the Delphi-based products, including many niche vertical-market products not prominent enough for the above lists.