Rub-a-dub-dub, three men in a tub
Rub-a-dub-dub is a nursery rhyme, and its oldest known printed version from the 14th century goes:

Hey! Rub-a-dub-dub! Ho! Rub-a-dub-dub! Three maids in a tub,
And who do you think were there?
The butcher, the baker, the candlestick maker,
And all of them gone to the fair!

Rub a dub dub,
Three men in a tub,
And who do you think they be?
The butcher, the baker,
The candlestick maker.
Turn them out, knaves all three!

The nursery rhyme is interpreted as describing otherwise respectable tradesmen attending a peep-show.

When Mitch tells her that a merchant named Keifaber, Stanley, and Shaw have all sworn to the stories regarding Blanche’s her shameful past in Laurel, Blanche says, “Rub-a-dub-dub, three men in a tub! And such a filthy tub!” to suggest that the men are liars whose word should not be trusted.

Source: http://www.answers.com/topic/rub-a-dub-dub-1<span
The Flamingo is the name of the hotel in Laurel that Blanche supposedly moves into after losing Belle Reve. It is a second-class hotel with a shady reputation, and it is known not to interfere with the private and social life of its guests. Blanche’s stay at this hotel links her to her promiscuity and scandalous past; Stanley is informed that even the management of such a sleazy hotel was “impressed” (99) by Blanche’s behavior that she was eventually asked to leave. However, Blanche claims the name of the hotel she stayed at was not called Flamingo, but Tarantula Arms instead.
Tarantula Arms
Tarantula Arms is the name of the hotel Blanche insists she stayed at and “brought [her] victims.” Tarantula refers to a specific family of spider that is usually very large, poisonous, and hairy. It is found anywhere between the southwestern U.S. and South America.

The motel “Tarantula Arms” may have symbolic importance, as its name represents the kind of life Blanche led during her stay there. Like a venomous spider, Blanche built a web of illusions and lured men into her motel room. (Tarantulas are also known to be nocturnal creatures.) The imagery of Blanche as a tarantula also connotes her to a noxious individual and an unwelcome presence anywhere.
Source: http://www.answers.com/topic/tarantula</span
Flores para los muertos

Corones para los muertos
Flores para los muertos” is Spanish for “flowers for the dead.” Corones para los muertos” literally means crowns for the dead, but a corona (singular), can also specifically be a circular arrangement of flowers worn on the head at funerals. Such flowers are widely presented on graves on Día de los Muertos, a Mexican holiday that celebrates the dead.

A blind Mexican vendor outside the Kowalskis’ building repeatedly utters these words as she offers Blanche flowers that are typically displayed at low-class Mexican funerals. Blanche responds with fear, yelling, “No, no! Not now! Not now!” (119), before slamming the door. The vendor’s act of offering flowers for the dead to Blanche is a symbolic gesture that suggests Blanche’s own demise is imminent. The Mexican woman appears after Blanche finally reveals to Mitch the truth about her affairs with men as well as with her seventeen-year-old student. Blanche’s dreams of a romantic, married life with Mitch are therefore shattered, and the death of her fantasies is symbolized by these funeral flowers.
A paddy-wagon is a slang term for a police car or a police vehicle used to transport large numbers of people who have been arrested. The term originated int he United States and its use dates to the beginning of the 1900s.
Source: http://www.answers.com/topic/paddywagon
Honky-tonk / Honky-tonk music
A honky-tonk is a type of bar common in the Southwestern and Southern United States that provides musical entertainment. Honky-tonks developed in the late 1800s and became associated mainly with lower class bars catering to men. Honky-tonks were rough establishments especially in the Deep South and Southwest, and sometimes served as centers of prostitution.

Honky-tonk music was a style of piano playing related to ragtime that emphasized rhythm rather than melody or harmony as the style evolved in response to an environment where the pianos were often poorly cared for, tending to be out of tune and having some nonfunctioning keys. The cheap out of tune piano sound adds a garish note to the scene in which Blanche dresses herself in a gaudy costume and entertains imaginary admirers.
Source: http://www.answers.com/topic/honkytonk
Fireman’s ball
Refers to a dance organized by the local fire brigade. The phrase connotes a cheap, humble sort of entertainment, which Stanley mocks Blanche of being invited to.