Katakana is the Japanese syllabary used for foreign loanwords, names, and emphasis. Use this free chart to learn all 46 characters with romaji.
Vowels
K-row
S-row
T-row
N-row
H-row
M-row
Y-row
R-row
W-row + N
Drill Katakana until it sticks
Charts are great for reference — but you'll learn faster with an interactive drill. InputDojo has a free katakana drill plus full Japanese reading lessons.