These are all the sites I know (and remember at the moment). Hope it's useful, specially for newbies

Link to Japanese sites at the end, courtesy of
moonlight[tabular type=3]
[row] [head]Site[/head] [head]Exchange[/head] [head]Language[/head] [head]Registration[/head] [/row]
[row] [data]
SC4Devotion[/data] [data]
LEX[/data] [data]English[/data] [data]Yes[/data] [/row]
[row] [data]
Simtropolis[/data] [data]
STEX[/data] [data]English[/data] [data]Yes[/data] [/row]
[row] [data]
SimPeg[/data] [data]
PLEX[/data] [data]English[/data] [data]Yes[/data] [/row]
[row] [data]
Simforum and
SimCity Plaza[/data] [data]
SimCityKurier[/data] [data]German[/data] [data]No[/data] [/row]
[row] [data]
Capital SimCity[/data] [data]
Descargas[/data] [data]Spanish[/data] [data]No[/data] [/row]
[row] [data]
ToutSimcities[/data] [data]
Téléchargements[/data] [data]French[/data] [data]No[/data] [/row]
[row] [data]
Simcity Polska[/data] [data]
Downloads[/data] [data]Polish[/data] [data]Yes[/data] [/row]
[row] [data]
Simcity China [/data] [data]
Here[/data] [data]Chinese[/data] [data]Yes (
follow this tutorial)[/data] [/row]
[row] [data]
Workingman productions[/data] [data]
Downloads and
SC4Tools[/data] [data]English[/data] [data]No[/data] [/row]
[row] [data]
Simcity Brazil[/data] [data]
SbEX[/data] [data]Portuguese[/data] [data]Yes[/data] [/row]
[row] [data]
City Builders Website[/data] [data]
CBEX[/data] [data]English[/data] [data]Yes[/data] [/row]
[row] [data]
Simmania[/data] [data]
Filecave[/data] [data]English[/data] [data]Yes[/data] [/row]
[row] [data]
SimCity Central[/data] [data]
Downloads[/data] [data]English[/data] [data]Yes[/data] [/row]
[row] [data]
Dmscopio BATs[/data] [data]
Download BATs ( most not available (some available over at Simtropolis)[/data] [data]English[/data] [data]No[/data] [/row]
[row] [data]
Simcity4 Mods[/data] [data]
Gizmo Downloads[/data] [data]English[/data] [data]Yes[/data] [/row]
[row] [data]
Mike's Props[/data] [data]<[/data] [data]English[/data] [data]No[/data] [/row]
[row] [data]
CSG Design[/data] [data]No[/data] [data]English[/data] [data]No[/data] [/row]
[row] [data]
Simphoni[/data] [data]
Here[/data] [data]English[/data] [data]No[/data] [/row]
[row] [data]
Japanese sites[/data] [data]<[/data] [data]Japanese[/data] [data]-[/data] [/row]
[row] [data][/data] [data][/data] [data][/data] [data][/data] [/row]
[/tabular]
Moderator Edit: Link Deleted