Online service Geni has added options to the Advanced Search interface to help you find profiles that previous searches may have overlooked. The first option lets you search names using soundex or metaphone to find profiles with alternate spellings. Each uses a different matching technology, so you can try the same search with each to see what works best for your particular search terms.
Next is the Match blank years option. When you enter a year search term, such as year of birth, your results will only include profiles that have a matching year. Check the Match blank years box to also include profiles that don't have a year entered. Similar profiles matches uses the match on blank years option to find all potential matches.
Similar profiles now search on maiden name and last name. You'll notice an OR search term in the last name field of these similar profile searches. You can use OR in any name field except for All Names to expand your search.
You can try these new features at http://www.geni.com.