Ruby, 215, 216, 218, 221, 224, 236, 237 chars
update 1: Hurray! It's a tie with JS Bangs' solution. Can't think of a way to cut down any more :)
update 2: Played a dirty golf trick. Changed each to map to save 1 character :)
update 3: Changed File.read to IO.read +2. Array.group_by wasn't very fruitful, changed to reduce +6. Case insensitive check is not needed after lower casing with downcase in regex +1. Sorting in descending order is easily done by negating the value +6. Total savings +15
update 4: [0] rather than .first, +3. (@Shtééf)
update 5: Expand variable l in-place, +1. Expand variable s in-place, +2. (@Shtééf)
update 6: Use string addition rather than interpolation for the first line, +2. (@Shtééf)
w=(IO.read($_).downcase.scan(/[a-z]+/)-%w{the and of to a i it in or is}).reduce(Hash.new 0){|m,o|m[o]+=1;m}.sort_by{|k,v|-v}.take 22;m=76-w[0][0].size;puts' '+'_'*m;w.map{|x,f|puts"|#{'_'*(f*1.0/w[0][1]*m)}| #{x} "}
update 7: I went through a whole lot of hoopla to detect the first iteration inside the loop, using instance variables. All I got is +1, though perhaps there is potential. Preserving the previous version, because I believe this one is black magic. (@Shtééf)
(IO.read($_).downcase.scan(/[a-z]+/)-%w{the and of to a i it in or is}).reduce(Hash.new 0){|m,o|m[o]+=1;m}.sort_by{|k,v|-v}.take(22).map{|x,f|@f||(@f=f;puts' '+'_'*(@m=76-x.size));puts"|#{'_'*(f*1.0/@f*@m)}| #{x} "}
Readable version
string = File.read($_).downcase
words = string.scan(/[a-z]+/i)
allowed_words = words - %w{the and of to a i it in or is}
sorted_words = allowed_words.group_by{ |x| x }.map{ |x,y| [x, y.size] }.sort{ |a,b| b[1] <=> a[1] }.take(22)
highest_frequency = sorted_words.first
highest_frequency_count = highest_frequency[1]
highest_frequency_word = highest_frequency[0]
word_length = highest_frequency_word.size
widest = 76 - word_length
puts " #{'_' * widest}"
sorted_words.each do |word, freq|
width = (freq * 1.0 / highest_frequency_count) * widest
puts "|#{'_' * width}| #{word} "
end
To use:
echo "Alice.txt" | ruby -ln GolfedWordFrequencies.rb
Output:
_________________________________________________________________________
|_________________________________________________________________________| she
|_______________________________________________________________| you
|____________________________________________________________| said
|_____________________________________________________| alice
|_______________________________________________| was
|___________________________________________| that
|____________________________________| as
|________________________________| her
|_____________________________| with
|_____________________________| at
|____________________________| s
|____________________________| t
|__________________________| on
|__________________________| all
|_______________________| this
|_______________________| for
|_______________________| had
|_______________________| but
|______________________| be
|_____________________| not
|____________________| they
|____________________| so
