Some of my solutions:

#### The one I like:

1.upto(100) do |i|
   a, b = i%3, i%5

   print "fizz" if a==0
   print "buzz" if b==0
   print i if a!=0 && b!=0
   puts
end

#### The first one, 4 mins, but not something I would leave on a page

100.times do |i|
   j = i + 1
   if j%15 == 0
     puts "fizzbuzz"
     next
   end
   if j%3 == 0
     puts "fizz"
     next
   end
   if j%5 == 0
     puts "buzz"
     next
   end
   puts j
end

# hmmm, that wasn't so good :-)

#### My one liner (and I spend quite some time to shorten it from 76  
to 70 chars, damn, but then again, I never tried to write as-short-as- 
possible-one-liners before)

1.upto(100){|i|a=(i%3==0?"fizz":"")+(i%5==0?"buzz":"");puts a[1]?a:i}