Dunno about spellings for actors, and I haven't been in this thread for a while so I'll put a new list.
Cloud- David Borneaz (Angel)
Barret- Whoever played John Coffey from The Green Mile
Tifa- Katie Holmes
Aeris- Eliza Dushku
Red XIII-voiced by Val Kilmer
Cait Sith- Brad Pitt
Vincent-Sean Connery
Cid- Bruce Willis
Yuffie- Dunno, but I suspect whoever plays Cho Chang in HP will fit pretty well given she'll be the right age, race, and should be athletic and upbeat/emotional.
Sephiroth- James Marsters (Spike in Buffy)
President Shinra - Arnold Schwarzenneger
Rufus-Leonardo DiCaprio
Heidegger- The Professor from Sliders
Scarlet-Michelle Pfeiffer
Reeve- Pierce Brosnan
Palmer-Danny DeVito
Hojo-Hugo Weaving
Reno- Colin Farrel
Rude- Samuel L. Jackson
Tseng- Christian Bale
Elena- The Girl in Two Guys and a Girl.
Don Corneo- John Goodman
Bugenhagen- Mr. Miagi
Shera- Jodie Foster