We have it every year! And in different places! I recommend it so much!
When you star planning, let me know! I'll help you!
And you posted this in the North America forum why?
Brasil info should be posted in the Central and South America forum. Also, the Brasilian carnival just took place and won't take place again for another year. (It takes place the week before Lent starts)., although it is true that the samba schools hold events all year long to raise money for their carnival parade costumes and floats.
P.S. I have used the spelling of Brasil as they spell it in Brasil, rather than the normal English spelling (Brazil).
[ Edit: Added PS ]
For those who may be interested In the Brasilian Carnaval, let me give you just a little bit of insight.
The Carnival period itself runs from the Friday before Lent starts until the day before Lent starts (this day is commonly referred to as "Fat Tuesday"). Lent always starts on Ash Wednesday which is 40 days prior to Easter. There are some groups in the city which run their own parties, some of which start as much as a week prior (for example, the Yacht Club normally holds theirs a week prior), and sometimes Sugarloaf Mountain (the Mountain in town that you go to the top via a tram system) does likewise.
The Carnival consists of a large numbers of parties, which run in the evenings. The most elaborate ones are held at the hotels around town, while the less elaborate ones are held at the many nightclubs around town. When I attended Carnaval, the largest one was at the National Hotel outside of town and was attended by many celebrities and also a few Arab sheiks and their entourages.
On Sunday night, starting around 7 PM, there is the first (and most famous) samba parade held in Rio. This parade normally runs until around 1 PM the following day. It consists of 8 samba schools, who are judged in 10 different categories--some of which are (1) floats, (2) greeters, (3) flag bearers, (4) song (each school writes a new song to play and sing to each and every year), (5) band, (6) movement and dance, (7) costumes, and 3 more I don't remember. The parade is always held every year in the Rio "Sambadome". The winner gets massive prizes, and the loser is relegated to the lower parade the following year. (The lower parade is held on Monday night--also runs from 7 PM to 1 PM the following day, and the winner of this parade moves up to the Sunday parade the following year). If you can't make it to the Sambadome, or simply can't handle watching and dancing to a parade for 18 hours, it is all shown on TV nationwide.
There is also lots of good fun to be had throughout the city as impromptu parades form all over the city for no reason at all, roving groups of gay guys and girls go up and down the beaches visiting sidewalk cafes and causing general laughter everywhere, and you will see romance in the air throughout the city as local citizens (Cariocas) believe that whatever happens during Carnaval doesn't count when it comes to your regular marriage/relationship--and thus craziness is generally encouraged. (kind of a "What happens in Vegas stays in Vegas view--only applied to the Brasilian cities of Rio (and also Recife and Salvador, where other large parades are held).
The city gets totally filled up, so if you plan to go, book early. Also be aware that the Carnaval is held in February or March, meaning that in South America it is in the hottest summer months. Thus, during the day most people are recovering from the party the night before by going to the beach or pools and soaking up the sun. If you go, have fun--that's really what Carnaval is all about.