A couple of days during May saw large hail fall across parts of central Indiana.
On May 10, thunderstorms dropped golf ball size hail on northeast sections of central Indiana:

Hail in Delaware County on May 10. Click to enlarge.
Below are reports from May 10:
PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
714 PM EDT TUE MAY 10 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0144 PM HAIL CICERO 40.12N 86.02W
05/10/2011 E0.50 INCH HAMILTON IN TRAINED SPOTTER
0146 PM HAIL 1 N CICERO 40.14N 86.02W
05/10/2011 E1.50 INCH HAMILTON IN TRAINED SPOTTER
0147 PM HAIL NOBLESVILLE 40.06N 86.03W
05/10/2011 E0.25 INCH HAMILTON IN TRAINED SPOTTER
0149 PM HAIL CICERO 40.12N 86.02W
05/10/2011 E1.75 INCH HAMILTON IN EMERGENCY MNGR
0202 PM HAIL 8 NE NOBLESVILLE 40.14N 85.92W
05/10/2011 M1.75 INCH HAMILTON IN AMATEUR RADIO
GOLF BALL SIZED HAIL COVERING THE GROUND...NEAR 246TH ST
AND BREHM RD.
0204 PM HAIL 6 SW ELWOOD 40.21N 85.92W
05/10/2011 E1.75 INCH HAMILTON IN TRAINED SPOTTER
0206 PM HAIL 5 NNE LAPEL 40.14N 85.81W
05/10/2011 M1.25 INCH MADISON IN TRAINED SPOTTER
2 ESE PERKINSVILLE.
0211 PM HAIL 7 S ELWOOD 40.17N 85.84W
05/10/2011 E1.75 INCH MADISON IN TRAINED SPOTTER
HALF DOLLAR TO GOLF BALL SIZE HAIL.
0213 PM HAIL 5 N LAPEL 40.14N 85.85W
05/10/2011 M1.75 INCH MADISON IN AMATEUR RADIO
IN PERKINSVILLE.
0215 PM HAIL 9 W ANDERSON 40.09N 85.86W
05/10/2011 M1.00 INCH MADISON IN TRAINED SPOTTER
AT 10 N AND 900 W.
0215 PM HAIL 3 S ALEXANDRIA 40.21N 85.68W
05/10/2011 M1.75 INCH MADISON IN TRAINED SPOTTER
0230 PM HAIL 6 N ANDERSON 40.18N 85.69W
05/10/2011 M1.50 INCH MADISON IN TRAINED SPOTTER
1 N PROSPERITY...LOTS OF HAIL COVERING GROUND.
0240 PM HAIL 2 N DALEVILLE 40.15N 85.56W
05/10/2011 M1.75 INCH DELAWARE IN TRAINED SPOTTER
FELL FOR FIVE MINUTES..COVERING GROUND.
0245 PM HAIL ANDERSON 40.09N 85.69W
05/10/2011 E1.00 INCH MADISON IN TRAINED SPOTTER
QUARTER SIZE HAIL COVERING GROUND.
0250 PM HAIL MUNCIE 40.20N 85.39W
05/10/2011 M1.75 INCH DELAWARE IN PUBLIC
NORTHWEST SIDE OF MUNCIE...0.5 MILES NW OF BALL STATE
CAMPUS.
0250 PM HAIL 7 NNE ANDERSON 40.19N 85.64W
05/10/2011 M1.00 INCH MADISON IN AMATEUR RADIO
0255 PM HAIL MUNCIE 40.20N 85.39W
05/10/2011 M1.25 INCH DELAWARE IN TRAINED SPOTTER
ON THE BALL STATE CAMPUS.
0348 PM HAIL 1 N EATON 40.35N 85.35W
05/10/2011 M1.00 INCH DELAWARE IN TRAINED SPOTTER
HAIL ONGOING.
0411 PM HAIL ALBANY 40.30N 85.23W
05/10/2011 M1.00 INCH DELAWARE IN AMATEUR RADIO
&&
On May 22, storms dropped hail up to 3 inches in diameter across parts of the area:

3 inch hailstone from near Camby (southwest of Indianapolis). Click to enlarge.
Below are reports from May 22:
PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
841 PM EDT SUN MAY 22 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0345 PM HAIL 3 SW CAMBY 39.63N 86.35W
05/22/2011 M1.00 INCH MORGAN IN NWS EMPLOYEE
0350 PM HAIL 2 S CAMBY 39.63N 86.31W
05/22/2011 E1.00 INCH MORGAN IN TRAINED SPOTTER
NEAR NORTH MADISON ELEMENTARY
0351 PM HAIL 1 S CAMBY 39.65N 86.31W
05/22/2011 U1.00 INCH MARION IN TRAINED SPOTTER
0352 PM HAIL 2 S MILROY 39.47N 85.47W
05/22/2011 E1.75 INCH RUSH IN LAW ENFORCEMENT
0355 PM HAIL CAMBY 39.66N 86.31W
05/22/2011 U2.00 INCH MARION IN TRAINED SPOTTER
0357 PM HAIL CAMBY 39.66N 86.31W
05/22/2011 M3.00 INCH MARION IN NWS EMPLOYEE
0400 PM HAIL 8 SW INDIANAPOLIS 39.69N 86.25W
05/22/2011 E1.00 INCH MARION IN TRAINED SPOTTER
COCORAHS REPORT OF 1 INCH HAIL
0400 PM HAIL 7 NE SHELBYVILLE 39.59N 85.68W
05/22/2011 M0.50 INCH SHELBY IN TRAINED SPOTTER
PEA TO HALF INCH HAIL.
0402 PM HAIL MORRISTOWN 39.67N 85.70W
05/22/2011 E1.75 INCH SHELBY IN PUBLIC
PUBLIC REPORT RELAYED THROUGH BORADCAST MEDIA.
0612 PM HAIL GREENWOOD 39.62N 86.11W
05/22/2011 M1.00 INCH JOHNSON IN NWS EMPLOYEE
0619 PM HAIL BEECH GROVE 39.72N 86.09W
05/22/2011 M0.50 INCH MARION IN TRAINED SPOTTER
PEA TO HALF INCH AT KEYSTONE AND RAYMOND AVES
INTERSECTION.
0621 PM HAIL 3 SSE INDIANAPOLIS 39.74N 86.12W
05/22/2011 M1.25 INCH MARION IN TRAINED SPOTTER
35-40 MPH WIND GUSTS ESTIMATED AS WELL. LOCATION OF
SPOTTER IS AT INTERSECTION OF HANNA AND KEYSTONE AVES.
0621 PM HAIL INDIANAPOLIS 39.78N 86.15W
05/22/2011 M0.75 INCH MARION IN TRAINED SPOTTER
AT SOUTH SPLIT OF INTERSTATE 65 AND 70 JUST SOUTH OF
DOWNTOWN INDIANAPOLIS.
0632 PM HAIL LAWRENCE 39.87N 85.99W
05/22/2011 E0.75 INCH MARION IN TRAINED SPOTTER
0650 PM HAIL 4 NE LAWRENCE 39.91N 85.93W
05/22/2011 M1.00 INCH HANCOCK IN PUBLIC
PENNY TO QUARTER SIZED HAIL FELL AT THE INTERESECTION OF
FOX AND OAKLANDON ROADS.
0814 PM HAIL KOKOMO 40.48N 86.13W
05/22/2011 M0.50 INCH HOWARD IN TRAINED SPOTTER
0820 PM HAIL GREENTOWN 40.48N 85.96W
05/22/2011 E1.00 INCH HOWARD IN TRAINED SPOTTER
VARYING SIZED HAIL UP TO QUARTER SIZE.