One of the most useful websites I know is the Epigraphik-Datenbank Clauss/Slaby (EDCS), maintained by the Katholische Universität Eichstätt-Ingolstadt. The English site is here. I use it nearly every day, and it rarely disappoints. These days, I am reorganizing my collection of photos, and it often helps me find the catalog numbers of the inscriptions.
Take, for instance, the photo to the right: an inscription from Lepcis Magna, which we photographed in 2006. There is no explanatory sign, but using the words “Lepcis Magna”, “Septimiae” and “splendidissimi”, it was easy to discover that this was inscription #607 of J.M. Reynolds & J.B. Ward Perkins, Inscriptions of Roman Tripolitania (1952 London). You will also find a photo of the inscription, which describes the setting up of a statue – the most expensive silver statue of Roman Africa, to be precise.
Some time ago, I used the EDCS to check which deities the ancients actually venerated. I obtained some remarkable results, which I would not have reached in so little time -one evening- if I had had to use those massive books of the Corpus Inscriptionum Latinarum – which I happen to love, but are less easy to use than the EDCS.