Roll 4d6, add up the total, compare to either of these tables for result. The odds are only off by a teeny bit (fudge is 144/1296 for each result, for this system all results fall between 141 to 146/1296 per). I realize this won't be for everyone, but some people may find it a bit easier than the 1,2- 3,4 5,6+ method.

Number rolled / Result
4   -1
5   -3
6   -4
7   -2
8   -3
9   -4
10   -4
11   -3
12   -2
13   -1
14   0
15   1
16   2
17   3
18   4
19   4
20   3
21   2
22   4
23   3
24   1

Result / Number rolled
-4   6   9   10
-3   5   8   11
-2   7   12   
-1   4   13   
0   14      
1   15   24   
2   16   21   
3   17   20   23
4   18   19   22