While Infocom created 30 some games during the golden age of Interactive Fiction in the 1980s, there are now thousands of Interactive Fiction titles available on the web at IFDB and elsewhere. Some are written in the traditional "old school" style, some push the boundaries of what Interactive Fiction is all about and no doubt some are complete crap. But there are some real gems among these, especially the games which place highly in the annual IF Competition.
If you've got old Infocom games, you can copy the Z-Machine data files (typically ending in .Z5 or similar) from old disks and run them with a new interpreter. You can also occasionally find old Infocom games for sale on Amazon and eBay. The best value is the "Lost Treasures of Infocom" or "Classic Text Adventure Masterpieces" CD ROM issued by Activision in the 1990s. If you're an advanced user, you can find these collections or similar bootlegs using Bit Torrent. (Just sayin'.)
Most Infocom sites do not publish the games, though they often have replicas of the boxes and supplemental materials. However, Activision did make the original Zork titles available for download and there is also a re-write of Deadline in Inform available on the IFDB.
I highly recommend using the IFDB as a way to find games that you might like. You can search using keyword tags, for example by different genres (horror, mystery, murder, sf, comedy etc). You can also browse by title, author, ratings and so on. Once you find something in a style you like, you may be surprised at just how many games there are!