Pit Girls

Belldandy dressed up as the Japanese version of this trope, the Race Queen.

She's holding the card, or handing out the trophies with accompanying bouquet. She's not participating in the sport. She is, however, not wearing very much.

Sex Sells, after all.

Compare with Hood Ornament Hottie.

Examples of Pit Girls include:

Anime and Manga

Future GPX Cyber Formula: Asuka started out as one and her role is later filled by Megumi and Satsuki in the last 2 OVAS. Rena Yuuki from the games counts as one as well.
Mirai Ozora has this role during a car race in Moldiver.
The Hentai manga Koisuru Race Queen by Chataro.
Hideyoshi Kinoshita of Baka to Test to Shoukanjuu is forced into this during a test battle he is not participating in. He tries to back out by pointing out that he isn't a girl, but this argument fails.

Films -- Live-Action

The Black Dahlia
The Rocky movies. In the first Rocky, the ring girl is dressed like the Statue of Liberty with silver makeup for the Bicentennial theme the champion Apollo Creed is promoting. A nice detail is her bound hair gets more unkempt as the fight (which most people didn't think would last three rounds) goes on for the entire fifteen. In Rocky II, for the rematch between Rocky and Apollo there are TWO ring girls, a black one and a white one wearing swimsuits, alternating each round.

Pro Wrestling

Valets are usually not this trope, although they may fall into it due to character neglect.
Mexican wrestling fed CMLL has "Ring Girls" accompany all their wrestlers to the ring.
WCW had the Nitro Girls. Although some of them eventually started participating in angles, for the most part they just danced.
WWF's Godfather was, during the Attitude Era, accompanied by "Hos". Although they generally did nothing, it's an interesting trivia note that Victoria debuted as the ho that the Right to Censor powerbombed through a table. In addition, another one of the hos was holder of the Hardcore Championship... for about a minute.

Sports

Formula One.
Race Queens (mostly in Japan).
The Olympic Games.
Round card girls are still a part of most fighting sports and are often featured prominently in local advertising.

Video Games

This is commonly featured in racing games.
- Cruis'n USA features one. The Nintendo 64 version gave her a way more conservative attire.
- Need for Speed Underground and Carbon have these during the starting countdown. Underground 2, however, upped the ante by occasionally using a pair of stage lesbians.
As well as the comedy boxing game, Facebreaker, which focuses on very Stripperifficly dressed round girls at the start of each round.
Parodied in Wade Hixton's Counter Punch, where the round card is carried by Mona, a frumpy, clearly jaded bar waitress.
Fight Night Round 3, at least, made sure to feature the ring girls between rounds. What's it mean when I got more entertainment from listening to the advice given to my boxer and his opponent?
Neverwinter Nights: Aribeth doesn't actually do anything other than stand around dispensing rewards and angsting until she does her Face Heel Turn (and keeps doing stuff after she dies).
Monday Night Combat features one actually named Pit Girl. She also has elements of a Wrench Wench.
Kiya carries the round cards during the boxing stage of Medi Evil 2. Oddly, she wears more clothes than usual.
Street Fighter managed to get by for 21 years without, but finally gave in, featuring them in one of the stages of Street Fighter IV alongside the usual round indicator.
The King of Fighters '97 is the only game in the series to have card girls, for some reason.
Crash Team Racing has four Petting Zoo People girls with parasols who present trophies to the winners of the races. They're not particularly dressed very skimpily, though they have Jiggle Physics.

Western Animation

Xandir takes on this role at least once in Drawn Together.
It was suggested that Kiva do this in one episode of Megas XLR due to the fact that the current round card girl was a squarish robot. In a bikini.
On the Family Guy episode where Meg joins the school newspaper, Lois worries that if Meg doesn't get into Brown University, she'll end up as a pit girl for bum fights.
A pit girl is featured in You're a Good Sport, Charlie Brown. If memory serves, the winner was supposed to get a kiss from her. Weird, in that nobody in the cast of Peanuts is over 9.
- What Could Have Been if Peppermint Patty won ...
In Wakfu, the first Gobbowl 3-episode arc features various Fanservice Extras of this kind, like the bikini-clad cowgirls ridding gobbals, or the two "bunny girls" (their costumes close to that of a Playboy Bunny, but with two little horns instead of rabbit ears) flanking the announcer.

Real Life

The tradition goes back to the horse races of the ancient Rome, where the Pit Girl was traditionally a part of the prize.