Many modern video cards have S-Video output, but their quality varies widely.
Recommendations: Pine XFX GeForce Ti4200 128Mb; "TV out on an ATI All-In-Wonder Pro 8mb AGP to work under Linux (which is pretty bad, though it was great under windows)"; "never had problems getting nVidia cards to work under Linux." "iMicro avermedia beats both; Radeon's Svideo out is much better than Geforce 4."