Here's some python for ya:
Code:
#!/usr/bin/env python
import sys
groups={}
while 1:
line = sys.stdin.readline()
if line == '':
break
try:
key,value=line.strip().split()
if not groups.has_key(key):
groups[key]=[value]
else:
groups[key].append(value)
except:
pass
keys=groups.keys()
keys.sort()
for key in keys:
print key,
print ",".join(groups[key])