Python (2.6), 1092 905 623 501 478 345 --> 318 characters
All comments welcome!
r=range;p=" __","/__ /|","| | |","|___|/"
l=map(int,raw_input().split())+[0];d=max(l)
g=[[" "]*(len(l)+1)*4 for i in r(d-min(l)+1)*2]
for i,e in enumerate(l):
for x,y in sorted([(i*4,(d-e+y-(0,1)[e<0])*2)for y in r(0,e,(1,-1)[e<0])])[::-1]:
for i in r(4):g[y+i][(x,x+1)[i<2]:x+6]=p[i]
for k in g:print ''.join(k)
