Great question! Currently we're sending out an email at the end of the day that will show you all posts for which you received useful votes. Unfortunately though there's no easy way to find these posts within your Trulia Profile.
This has bugged me for quite some time and I'm glad you brought it up so I can let our team know that it's something the Trulia Voices Community wants. If anyone else would like to be able to easily locate their Useful and Best Answers within their Trulia Profile, post a comment here and make your Voice heard!