tolong, a faster implementation of reshape long, is now available on ssc.
Type ssc install tolong and afterwards help tolong for details.

The syntax is sightly different from reshape long as tolong supports three kinds of stubnames

# matches numeric j
@ matches string j
* matches both string and numeric j

thus

tolong x is equivalent to reshape long x
tolong x# is equivalent to reshape long x@
tolong x* is equivalent to reshape long x@, string
tolong x@ has no reshape long equivalent

tolong also supports renaming on-the-fly as in

tolong height = h* weight = w*

tolong compares favorably in terms of speed against the user-written
fastreshape, sreshape, and greshape. The timings below were run in Stata/MP4.

Code:
1,000,000 observations

(1) reshaping numeric a1-a9 b1-b9 c1-c9 d1-d9
(2) reshaping numeric a1-a9 b1-b9 c1-c9 d1-d9 and string e1-e9 f1-f9
(3) reshaping numeric a1-a9 b1-b9 c1-c7 d1-d2
(4) reshaping numeric a1-a9 b1-b9 c1-c7 d1-d2 and string e1-e6 f1-f3

command           (1)     (2)     (3)     (4)
----------------------------------------------
reshape long    18.91   26.51   15.71   21.45
fastreshape      9.58   11.07       +       +
sreshape        10.45   12.50    9.64   11.29
greshape         1.50    2.54    1.57    3.80
tolong           1.59    5.34    1.61    2.41
----------------------------------------------
+ fastreshape does not support unbalanced j
As above but the data contains 20 numeric variables and 5 string variables that
are constant within id.

Code:
command           (1)     (2)     (3)     (4)
----------------------------------------------
reshape long    37.51   51.85   38.22   46.20
fastreshape     19.15   21.18       +       +
sreshape        14.80   17.52   13.97   16.62
greshape         7.17    7.50    7.13    7.53
tolong           2.35    6.27    2.66    5.08
----------------------------------------------
+ fastreshape does not support unbalanced j
Lastly, an extreme case with only 10 observations

Code:
(1) reshaping numeric x1-x10000
(2) reshaping numeric x1-x100000

command           (1)       (2)
--------------------------------
reshape long    77.12         +
fastreshape     29.72   2916.03
sreshape            *         *
greshape         7.04         ^
tolong           0.03      0.54
--------------------------------
+ "variable _j takes on too many values" error
* "invalid numlist has too many elements" error
^ "characteristic contents too long" error