Draw Concentric ASCII Hexagons
Python - 251, 240, 239 228

l=input()+[0];m=max(l);A=abs;R=range
for j in R(2*m+1):print''.join([[' \\'[(A(j-i+m-1)/2.in l)*(2*m-i)/(j-m-.5)&gt;1],'/'][(A(3*m-i-j)/2.in l)*(i-m-j+.5)/(j-.5-m)&gt;0],'_'][(A(m-j)in l)*(A(2*m-i-.5)&lt;A(m-j))]for i in R(4*m)).rstrip()




Alternative approach (251):

l=input()+[0]
l.sort()
m=max(l)
M=2*m
s=[[' ']*m*4for j in' '*(M+1)]
for i in l:
 I=2*i;s[m-i][M-i:M+i]=s[m+i][M-i:M+i]='_'*I
 for k in range(i):K=k+1;s[m-k][M-I+k]=s[m+K][M+I-K]='/';s[m-k][M+I-K]=s[m+K][M-I+k]='\\'
for t in s:print''.join(t).rstrip()