Hey this will depend largely on your budget. but in general Most long boards will work well for cruising but I'd still recommend a deck size between 36-42 inches IMO its better to get a board that has at least 1 kick tail and some concave.That way if you ever want to learn any tricks or slides you can. (and you probably will)
Here are some links to boards I like:
http://www.arborcollective.com/skate/boards/view/449675/catalyst-38
http://www.nelsonboards.com/tempest.html
http://www.daddiesboardshop.com/landyachtz-40-drop-carve-longboard-skateboard-complete-2012
http://www.daddiesboardshop.com/bustin-boards-boombox-longboard-skateboard-complete
http://www.daddiesboardshop.com/db-longboards-the-cosmonaut-complete
example of a dropped deck board
http://www.landyachtz.com/D25.cfm?PID=534
and remember a more expensive deck does not mean a better quality deck, you should look up reviews and ratings before making your final purchase
good luck :p