Pre-Christian Celtic Inscriptions

Most of these are housed at the Quellentexte, Artikel site at Keltologie, a German site.

Gaulish:
Berne zinc tablet/Gobannus tablet
Carjac Inscription (RIG L-49)
Chamalières Tablet (RIG L-100)
Châteaubleau Tablet (RIG L-93)
Coligny Calendar
Larzac Tablet (RIG L-98)
Lezoux Tablet (RIG L-66)
Martialis Inscription (RIG L-13)
Parisi Boatmen Pillar
Rom, Deux-Sèvres Tablet (RIG L-103)
Spinnwirtelaufschriften Tablet (RIG L-111-122)
Vaison Tablet
Endlicher's Glossary; a photo can be seen here

Celt-Iberian:
Botorrita I*
Botorrita III
Botorrita IV
Botorrita: another version
Peñalba de Villastar
Torrijo del Campo

* Botorrita II is apparently a Latin tablet

Cisapline Celtic
Aranno Fragments (S 1)
Banco Inscription (S 2)
Bilingual Tablet (RIG II.1, 45-51)
Davesco (S 3)
Giubiasco 01 (S 4)
Giubiasco 02 (S 5)
Giubiasco 03 (S 5)
Giubiasco 04 (S 6)
Giubiasco 05 (S 8)
Giubiasco 06 (S 9)
Giubiasco 07 (S 10)
Giubiasco 08 (S 11)
Giubiasco 09 (S 12)
Giubiasco 10 (S 13)
Giubiasco 11 (S 14)
Giubiasco 12 (S 15)
Giubiasco 13 (S 16)
Gudo, Piano Magadino (S 17)
Maroggia (S 18)
Mauergraffiti of Milan (S 104)
Mesocco (S 19)
Mezzovico (S 20)
Ponte Capriasca (S 20bis)

East Celtic (Norish)
Grafenstein
Ptuj (Pettau, Poetouio)

Lepontic:*
Castelletto Ticino Inscription (S 113bis)
Davesco Inscription (S3)
Ornavasso Inscription (S 128)
Prestino Inscription (S 65)
Vergiate Inscription (S 119)
Lepontic Vessel

*There is some question as to whether Lepontic is Celtic, or if it's a relative of Ligurian.

Controversial:
Glozel Tablets