I've tried that [before], but with multiple parameters, I simply got zero results. I then enclosed the site:foo OR site:bar within parentheses, leaving the rest of the query outside parentheses. Whichever site:foo came first would be matched, but only it appeared to be matched. Subsequent site:bar, etc. parameters did not produce any matches in the results.
I'll have a look at your links, in a minute -- probably should have done that first.
EDIT: Well, your second link sure works. I wonder what I was doing wrong. When I saw someone else('s or s') comments online to the effect that it didn't work, I assumed that was why my own experience failed.
I'm in serious need of some coffee, at the moment. Thanks for correcting my mis-impression; I look forward to straightening it out in my mind and taking advantage of this feature.
site:http://news.ycombinator.com OR site:stackoverflow.com <query>
I don't know if there's a max # of sites you can add. I tried it with three and it seemed to work great.
http://www.google.com/search?q=site:searchengineland.com+OR+...
(Yes, I did an ego search. Isn't that the best way to know if the results are likely accurate? :)
If there's a set of sites you want to search through often, you can set up a custom search engine for what you describe. For instance, see this page:
http://www.toddnemet.com/