Here’s a list of search engine services available and optimized for mobile device screens. I have provided briefed about every provider’s offering.

1) Google Mobile- can be accessed at mobile.google.com- provides XHTML and basic WML search, Google Maps, Google News, GMail Mobile, Local Search and free SMS

2) Ask Mobile- can be accessed at mobile.ask.com- uses Skweezer to compress data- provide Driving or Walking directions, Image search, Business Listings, Mapping Service, Weather, Bloglines blog search, Area codes, Currency Conversion, Horoscope and Time zones

3) Yahoo! Mobile- can be accessed at mobile.yahoo.com- provides web search, image search, local search, SMS search, Yahoo mail, yahoo messenger, alerts and other Yahoo! network services

4) Windows Live Mobile- can be accessed at mobile.live.com- provides Mail, Search beta, Spaces, Local, Live.com beta, MSN.com beta, MSNBC News, FOX Sports, Weather, Money, Entertainment

5) AOL Mobile- can be accessed at mobile.aol.com- provides AOL and AIM Mail, CityGuide (set your location and find a local services), MovieFone, AOL Feed Reader, MapQuest, AOL Pictures
News, Weather, Sports, Entertainment

Apart from this, there exist other search services/softwares for mobiles which I will update/cover some other time.