Udell is author of Practical Internet Groupware, published in 1999 by O'Reilly Media, and is an advisor to O'Reilly's Safari Tech Books Online. He wrote the column "Tangled in the Threads" for Byte.com from 1999–2002, and continues to be an active blogger. In this context he published a screencast illustrating how Wikipedia articles evolve, using Heavy metal umlaut as an example. A major focus of much of his writing is the question of how to enable non-experts to find data (often on the internet) and utilize in new ways.
He created the LibraryLookup bookmarklet project, which makes it easier for people to discover if their local library has a copy of a given book.