Atlas of the Hillforts of Britain and Ireland
English to Old Norse Dictionary
Sketches in Erris and Tyrawly - West Irish Ruins
Callanish Sites
RCAHMS: 9th report monuments in the outer Hebrides, Skye and the Small Isles
Saints in Scottish Placenames
OS 6-Inch Maps 1854
OS Name Book Ross and Cromarty (includes Lewis)
Skye's Hidden Heritage - Macaskills of Rudha an Dunain
Gaelic Place Names
Ardveg Stalking Article
Bill Cowie's Blog (South Rona)
Comann Eachdraidh Uig (Uig Historical Society - Lewis)
Discovery & Excavation Scotland Journals
Geograph UK
Hebridean Air Services
Hebrides Cruises (Elizabeth G/Rob Barlow)
Hebrides Fish 'N' Trips (boat trips - Lewis Mackenzie)
Hidden Hebrides
History of Rona
Ireland's Sile-na-Gig (Sheela-na-Gigs of Ireland)
Island Castles of Scotland (Photostream)
Islands Book Trust
Island of Boreray (Jerry Cox) - appears inactive
Islay Blog (Armin Grewe)
IslayInfo Blog
Isle of Tiree
John Humphries' blog
Lismore Accomodation
Lismore Gaelic Heritage
Love Scottish Islands
My Geograph Page (Grid-Square Photos)
Northern Light Cruising Company (Mark Henrys)
Old OS Maps of Scotland
Pairc Historical Society
The Papar Project (Hebrides Page)
Paul Camilli's Blog (Raasay)
Place Names of Skye
Poplar Diver
Proceedings of the Society of Antiquaries of Scotland
Ravenspoint Centre (Pairc)
Saints and Stones
Scottish Anchorages
Scottish Islands Explorer
Sea Harris
Seattle Gaelic Society
South Rona
Stravaiging Around Scotland
Stylized Beehive
Wild Lochaber

Photo Location Tools
Plot photo coordinates on GoogleEarth
OS Grid to Lat/Long Converter
Lat/Long Decimal to Deg:Min:Sec Converter
Tool to extract Photo GPS coordinates (Lat/Lng) to a csv file

With some editing, the csv file created by the above tool can be converted to OS Grid using the following tool:
OS Batch Conversion Tool - Convert Photo GPS coordinates to OS Grid