JoyceImages.com. You can browse, chapter-by-chapter or see the whole of it all at once.
It takes the Vintage corrected text of Ulysses and gives images and context, with section and line references. For example this picture post card is used to illustrate the text "They halted, looking towards the blunt cape of Bray Head that lay on the water like the snout of a sleeping whale." (U1.181)
The site itself doesn't reveal much about its origins, just this statement in the footer: "JoyceImages.com is maintained by Aida Yared" along with an email address. There's also little information on Yared's profile on Amazon.
Tony Thwaites' Ulysses Dublin Tour complements JoyceImages by giving photos taken in 1004. The Joyce Foundation links page includes it along with a lot of other interesting ones.
At JoyceImages.com, the Boulanger reference reads:
"M. Millevoye," (U3.233)
Lucien Millevoye (1850-1918) was a French journalist and politician. He was the editor of 'La Patrie' and a supporter of Général Boulanger. Maud Gonne had a love affair with him in France (he was married). They had 2 children, Georges Silvère (1890-1891), and Iseult Lucille Germaine (1894-1954). Back in Ireland, Gonne passed Iseult off as her adopted niece.
One of the best images on joyceimages.com is a contemporary map of Dublin on which you can trace the wanderings of Bloom and Dedalus. It's in large format so you can see lots of locations in detail