Homesnap - a quick and fun online search tool plus mobile app (ios and Android).
You can: search by area (e.g. Perry Park or Bow Mar -- very cool, try it!), your location (using GPS), snap a photo of a home and see details, send messages, and share and rate properties.
Additionally, you can view recent sales, live market activity, and market information. Great stuff!
You can't: select an area on the map by shape, make notes, or hide properties, and I would not be able to customize any searches for you. Search criteria are rather limited but the highpoints are included (beds, baths, price, your rating, etc.). Limited to residential homes (in other words no land, ranches, etc.)
FREE and easy to use. On you laptop/desktop or a mobile device (apps for iOS and Android).
See also: other MLS Search Options