two (okay I lied, should be there) problems with your code
i, your input longitude should be negative to be within the boundary you defined for your basemap, so add this after before converting to x and y
longitude = [-i for i in longitude]
ii, your coordinate conversion line is wrong, you should swap lon and lat in the argument list
x, y = m(longitude, latitude)
instead of
x, y = m(latitude,longitude)
EDIT:
okay, the second question that OP posted in the comments, please check the complete code below and please pay attention to the changes I've made compared to yours
# Last-modified: 21 Oct 2013 05:35:16 PM
import numpy as np
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
import csv, os, scipy
import pandas
from PIL import *
data = np.loadtxt('louisianastormb.csv',dtype=np.str,delimiter=',',skiprows=1)
'''print data'''
fig = plt.figure(figsize=(12,12))
ax = fig.add_axes([0.1,0.1,0.8,0.8])
m = Basemap(llcrnrlon=-100.,llcrnrlat=0.,urcrnrlon=-20.,urcrnrlat=57.,
projection='lcc',lat_1=20.,lat_2=40.,lon_0=-60.,
resolution ='l',area_thresh=1000.)
m.drawcoastlines(linewidth=0.5)
m.drawcountries(linewidth=0.5)
m.drawstates(linewidth=0.5)
# m.bluemarble(ax=ax)
# Creates parallels and meridians
m.drawparallels(np.arange(10.,35.,5.),labels=[1,0,0,1])
m.drawmeridians(np.arange(-120.,-80.,5.),labels=[1,0,0,1])
m.drawmapboundary(fill_color='aqua')
color_dict = {'AUDREY': 'red', 'ETHEL': 'white', 'BETSY': 'yellow','CAMILLE': 'blue', 'CARMEN': 'green','BABE': 'purple', }
colnames = ['Year','Name','Type','Latitude','Longitude']
data = pandas.read_csv('louisianastormb.csv', names=colnames)
names = list(data.Name)
lat = list(data.Latitude)
long = list(data.Longitude)
colorNames = list(data.Name)
#print lat
#print long
lat.pop(0)
long.pop(0)
colorNames.pop(0)
latitude= map(float, lat)
longitude = map(float, long)
# added by nye17
longitude = [-i for i in longitude]
# x, y = m(latitude,longitude)
x, y = m(longitude,latitude)
# convert to numpy arrays
x = np.atleast_1d(x)
y = np.atleast_1d(y)
colorNames = np.atleast_1d(colorNames)
#Plots points on map
for colorName in color_dict.keys():
plt.plot(x[colorName == colorNames],y[colorName == colorNames],linestyle ='-',label=colorName,color=color_dict[colorName], linewidth=5 )
lg = plt.legend()
lg.get_frame().set_facecolor('grey')
plt.show()