I compiled some programming language popularity statistics in April 2009October 2009October 2010September 2011August 2012 and Februrary 2013. Here’s an update for September 2013:

I made a number of Google searches of the forms below and summed the results:

"implemented in <language>"
"written in <language>"
"developed in <language>"
"programmed in <language>"

I've divided the table into sections based on large percentage drops from one language to the next.

|------+-----------------+------------+----------+-------|
| Rank | Language        | # Results  | Previous |  Rank |
|      |                 |            |     Rank | Delta |
|------+-----------------+------------+----------+-------|
|    1 | PHP             | 54,516,000 |        1 |       |
|------+-----------------+------------+----------+-------|
|    2 | C               | 31,536,000 |        2 |       |
|    3 | Python          | 24,700,000 |        4 |     1 |
|    4 | C++             | 22,697,000 |        3 |    -1 |
|    5 | C#              | 20,309,000 |        5 |       |
|------+-----------------+------------+----------+-------|
|    6 | Java            | 13,314,000 |        7 |     1 |
|    7 | Perl            | 11,588,000 |        6 |    -1 |
|------+-----------------+------------+----------+-------|
|    8 | JavaScript      |  6,389,000 |        8 |       |
|    9 | Ruby            |  4,710,000 |        9 |       |
|   10 | FORTRAN         |  4,167,000 |       11 |     1 |
|------+-----------------+------------+----------+-------|
|   11 | Lisp Family (1) |  2,444,860 |       10 |    -1 |
|   12 | ML Family (2)   |  1,787,586 |       16 |     4 |
|   13 | Lua             |  1,653,100 |       15 |     2 |
|   14 | Prolog          |  1,389,900 |       22 |     8 |
|   15 | Smalltalk       |  1,003,200 |       27 |    12 |
|   16 | R               |  1,000,700 |       13 |    -3 |
|   17 | COBOL           |    856,500 |       18 |     1 |
|   18 | Lisp            |    835,600 |       12 |    -6 |
|   19 | Erlang          |    808,400 |       17 |    -2 |
|   20 | Haskell         |    798,700 |       19 |    -1 |
|------+-----------------+------------+----------+-------|
|   21 | (S)ML (3)       |    559,186 |       23 |     2 |
|   22 | Common Lisp     |    548,100 |       20 |    -2 |
|   23 | Go              |    490,230 |       28 |     5 |
|   24 | Scheme          |    487,100 |       25 |     1 |
|   25 | Scala           |    481,100 |       24 |    -1 |
|   26 | OCaml           |    429,700 |       21 |    -5 |
|   27 | Clojure         |    352,000 |       30 |     3 |
|------+-----------------+------------+----------+-------|
|   28 | Forth           |    230,630 |       31 |     3 |
|   29 | Racket          |    222,060 |       33 |     4 |
|   30 | CoffeeScript    |    205,809 |       29 |    -1 |
|------+-----------------+------------+----------+-------|

(1) combines Lisp, Common Lisp, Scheme, Clojure & Racket
(2) combines Haskell, (S)ML & OCaml
(3) summed separate searches for standard ml, sml & ml