I can vouch for re2 - if you need to run a lot of regexps, or run user-supplied regexps, or run non-trivial regexps on user-supplied arbitrary data, re2 will save your application from certain death if you use pcre. Google "catastrophic backtracking" if you don't believe me.<p>Also, even though it doesn't say that Russ uses it, he probably must one way or the other working at Google, I highly recommend another google code project - protobuf.