Ill start :

Super League

Bradford ( Odsal, Valley Parade )
Castleford
Harlequins ( also Brentford, Charlton and Bridgend )
Huddersfield
Hull FC ( KC Stadium, Boulevard )
Hull KR ( Craven Park )
Leeds
Salford
St Helens
Wakefield
Warrington ( Wilderspool, Halliwell Jones )
Wigan ( JJB, Central Park )

National Leagues

Halifax
Featherstone
Keighley
Leigh
Sheffield
Widnes

Others -

Old Trafford
Wembley
Millenium Stadium

Did hull fc play london broncos at leicester?

Yes along with Bradford.

Been to a few for football, but here are the RL ones

Super League
Bradford Bulls
Castleford Tigers
Celtic Crusaders
London Broncos (Griffin Park)
Huddersfield Giants (Galpharm)
Hull FC (KC)
Hull KR
Leeds Rhinos
St. Helens
Salford City Reds
Wakefield Trinity
Warrington Wolves (Wilderspool, HJ)
Wigan Warriors (Central Park, JJB)

"National Leagues"
Barrow Raiders
Batley Bulldogs
Doncaster (Belle Vue, Keepmoat)
Featherstone Rovers
Halifax (The Shay)
Leigh Centurions (Hilton Park, LSV)
Sheffield Eagles (Don Valley)
Toulouse Olympique (Blagnac)
Whitehaven
Widnes Vikings
Blackpool Panthers (Bloomfield Road, Fylde RUFC - does Victory Park count?)
Dewsbury Rams
Keighley Cougars
London Skolars
Oldham Roughyeds (Hurst Cross, Boundary Park)
Rochdale Hornets
Swinton Lions (Gigg Lane, Moor Lane, Sedgeley Park)
York City Knights

Others
Elland Road
Old Trafford
Reebok Stadium
Ewood Park

been to all them Plus
York new and old ground.
Whitehaven,Workington,Batley,Dewsbury,Barrow,Doncaster(all 4 of there ground),Murryfeild,Swinton,Hunslet,Bramley,Oldham,Rochdale,Keithley,
Liverpool Fc, Isle of man, Paris.Elland road,Blackpool i think there is more but i can not remeber them all.

The Royal Dublin Showground anyone?

Wigan - Central Park & JJB Stadium
Warrington - Halliwell Jones
Wakefield - Belle Vue
Leeds - Headingley
Huddersfield - Galpharm
Halifax - Thrum Hall
Castleford - The Jungle
Hull FC - KC Stadium
Sheffield - Don Valley & Bramhall Lane
Doncaster - Belle Vue

Also watched at:
Wembley (Old & New), Twickenham, Maine Road, Reebok, Elland Road, Old Trafford, Murrayfield

Knowsley Road
New Craven Park
Hedingley
The Stoop
The Valley
Griffin Park
Galpharm Stadium
Belle Vue
KC Stadium
Boulivard
Wheldon Road
JJB Stadium
Central Park
Wilderspool
Halliwell Jones Stadium
Odsal
Valley Parade
Stade Aime Giral
Stade Gilbert Brutus
Willows
The Shay
Thrum Hall
Stobart Stadium
Chris Moyles Stadium
Craven Park
Recreation Groud
Hilton Park
Don Valley Stadium
Gateshead International Stadium
Boundary Park
South Leeds Stadium
Derwent Park
Old Trafford
Wembley
Murrayfield
Millenium Stadium
(Cardiff Arms Park)
Rodney Parade
Charlety Stadium
Stade d'Albert Domec
Elland Road
Sydney Football Stadium
OKI Jubille Stadium
Reebok Stadium
City of Manchester Stadium

Erm I was a bit of a ground collector

Super League
Bradford Bulls - Odsal and Valley Parade
Castleford Tigers
Fulham/London Broncos/Quins - Stoop, Griffin Park, The Valley, Craven Cottage, Leicester RFU, Bridgend RFU, Barnet Copthall, Tynecastle, Wealdstone F.C, Stamford Bridge, Chiswick Poly, Hendon, Crystal Palace and Broadfield Stadium.
Huddersfield Giants - Galpharm and Fartown
Hull FC - KC and Boulevard
Hull KR - New and Old Craven Park
Leeds Rhinos
St. Helens
Salford City Reds
Wakefield Trinity - Oakwell and Belle Vue
Warrington Wolves - Wilderspool and HJ
Wigan Warriors - Central Park and JJB

"National Leagues"
Batley Bulldogs
Bramley - McClaren Field, Headingley and Clarence Field
Blackpool - Bloomfield Road
Carlisle Border Raiders - Brunton Park and Sheepmount Stadium
Chorley Borough
Dewsbury - Crown Flatt and Mount Pleasant
Doncaster - Belle Vue and Tattersfield
Gateshead
Halifax - Shay and Thrum Hall
Highfield
Hunslet - Elland road and South Leeds Stadium
Keighley Cougars
Lancashire Lynx - Deepdale
London Skolars
Leigh Centurions - Hilton Park
Nottingham Outlaws - Harvey Haddon Stadium
Oldham Roughyeds - Watersheddings and Boundary Park
Prescott Panthers - Valerie Park
Scarborough Pirates - McCain Stadium
Sheffield Eagles - Don Valley and Oakwell
South Wales - Cardiff Arms Park
Swinton Lions - Gigg Lane and Park Lane
Trafford Borough
Whitehaven
Workington
Widnes Vikings
York City Knights - Huntingdon, Clarence Street, The Crescent

Others
Elland Road
Wembley
Loftus Road
Sixfield Stadium
Burnden Park
Reebok
Reading FC
Vicarage Road
Murrayfield
Millennium Stadium
Old Trafford
Twickenham
Glasgow Anniesland
Anfield Liverpool

There will be more when I can remember them

Super League

Odsal, Bradford
The Jungle, Castleford
Galpharm, Huddersfield
Headingley, Leeds
The Willows, Salford
Belle Vue, Wakefield
Halliwell Jones, Warrington

National Leagues

Mount Pleasant, Batley
The Shay, Halifax
Chris Moyles Stadium, Featherstone
Cougar Park, Keighley
Hilton Park, Leigh
Don Valley Stadium, Sheffield
Stobart Stadium, Widnes
Keepmoat Stadium, Doncaster
Crown Flatt, Dewsbury

Others -
Elland Road, Old Trafford (although not for rugby)