If you know the response curve of your microphone (a printed graph of which is included with any mic worth its salt), you can enter the calibration data yourself by hand. The files are very simple ascii text files.

The SpectraLAB software comes with pre-made calibration files for a few mics. They are:

AKG 1000
EV 257B
Shure SM57
Shure SM58
Radio Shack Mic (part number 33-3007)

I'm set, because I have a friend who owns several SM58's. /me is going to be doing some RTA here pretty darn soon. I'm excited.

The calibrated file for the radio shack mic looks like this: 

; Radio Shack low cost condenser mic (P/N 33-3007)

0	-50.0

40	-7.5

50	-7.0

80	-6.0

100	-6.0

120	-5.0

200	-3.5

300	-2.8

400	-2.0

1000	0.0

1100	0.8

1300	0.2

2000	1.0

3000	1.5

4000	1.8

5000	2.0

6000	2.2

7000	2.5

8000	2.4

9000	1.0

9500	0.0

10000	0.0

12000	-0.5

13000	-4.0

15000	-3.0

18000	-2.5

20000	-3.0
_________________________
Tony Fabris