sRGB or RGB?
I would amend the above advice to say:
If you only intend to send your images to a lab that doesn't use color profiles (i.e., doesn't read embedded color profiles), then yes, work in sRGB. It will simplify your life and keep your colors good.
However, if intend to send your images to a lab that does support color profiles (e.g., WHCC, Calypso, West Coast Imaging) or print them on an inkjet printer, then use a working color space such as Adobe RGB or ProPhoto RGB. Modern inkjets and papers DO have areas where the color gamut significantly exceeds sRGB, particularly the greens and blues. These differences are not subtle. Using sRGB in these cases will prevent you from accessing the full range of colors the devices are capable of producing.
So in summary: my rule of thumb is, if you plan to send to a lab that doesn't use color profiles, use sRGB. Otherwise, use Adobe RGB or ProPhoto RGB.