Don't have a "booking" recommendation, but the one time I went on a cruise via Carnival it was super cheap and one of the times of my life.
Heck now that I think about it, I paid less for the entire vacation (cruise, food, and way there and back) than I do for a months rent.
$350 for 4 day 3 night cruise to Cozumel Island, MX Paid $150 for greyhound from WV to Houston, TX + cab to/from bus to dock, since I didn't drink alcohol or pop drinks were free. Spent another $100 or so there on food and mostly picking up custom handcrafted chess boards. _
That is on the cheaper end, you can get a LOT of similar or better trips via AAA or a handful of local travel agents. Make sure to post a couple pics here on TT when you get back :)