Living expenses in Beirut can be compared to other cities in semi-developed countries like Bangkok or Taipei (I'm sure their are others... so add you comments bellow!).  It is not expensive, but also not cheap.  Lebanese lira and dollars are used interchangeably at the exchange rate of 1500 LBP/$1... both currencies can be used anywhere.

Apartment: $200-300 (shared) - $400-800 (private)... check our housing FAQ for more info.  In general Lebanese do not live outside their homes until married... so it is pretty hard to find a Lebanese roommate to practice your Arabic.

Food: sandwich $2-$5, sit-down meal $8 and up, groceries are cheap if you buy regular Lebanese things - Western and Eastern items are expensive.

Transportation: regular taxi $4 and up (depending on how far),  "service" shared taxi $1.33 (2,000 LBP), bus $.66, airport taxi $10-$20 (depending how good your Arabic is :)

Entertainment: beer $2-$5, wine $4-$8, movie $6, concerts $15-$35 (regular tickets)