Whenever you need to search for something it helps to imagine what you will see on the actual pages that the search engine will include in the results.
Let’s design Boolean strings to look for lists with email addresses and possibly phone numbers.
We would be looking for Excel or PDF files, or maybe CSV, or Doc, or html; thus, part of the string (on Google or Yahoo) would be filetype:xls OR filetype:PDF… It might be easier to review the results if we use a separate search string for each type.
We imagine that the lists we are going to find will have some or all of the words: name (possibly first, last), email (or e-mail), phone (or telephone, or contact), title, company. (Add or remove words to/from your search string depending on the results.)
If we are looking for lists with emails, we might imagine that some emails would be of a “public” type, so including gmail.com OR hotmail.com OR yahoo.com etc. may be a good idea.
If we have several target companies in mind and think we might locate a list of attendees, or members, or contarctors with representatives from those companies, we might look for, say, oracle.com OR cisco.com etc.
Similarly, if we know the target titles, we may try including them in the string, as an example, write mechanical OR electrical engineer OR consultant, etc.
We might also play with the idea that the pages to be found would have one of the words list, directory, attendees, participants, members, etc. either in the title or in the URL of the page. Trying these guesses separately might be helpful, not to clutter the search strings.
If it makes sensse to only look at recently published lists, that can be arranged on Google with the “options” (on the left).