Well, most other answers here refer to
sort -n
However, I'm not sure this works for negative numbers. Here are the results I get with sort version 6.10 on Fedora 9.
Input file:
-0.907928466796875
-0.61614990234375
1.135406494140625
0.48614501953125
-0.4140167236328125
Output:
-0.4140167236328125
0.48614501953125
-0.61614990234375
-0.907928466796875
1.135406494140625
Which is obviously not ordered by numeric value.
Then, I guess that a more precise answer would be to use sort -n but only if all the values are positive.
P.S.: Using sort -g returns just the same results for this example
Edit:
Looks like the locale settings affect how the minus sign affects the order (see here). In order to get proper results I just did:
LC_ALL=C sort -n filename.txt