The Open Guide to London: the free London guide

		Tube interchange	Mainline service
north
[Walthamstow Central]?			WAGN [Chingford line]?
[Blackhorse Road]?			Silverlink Barking line
Tottenham Hale			WAGN services to Hertford East, Bishops Stortford and Cambridge
[Seven Sisters]?			WAGN services to Enfield Town, Bishops Stortford and Cambridge
Finsbury Park		Piccadilly Line	WAGN GN Electrics Line and services to Hertford North and Welwyn Garden City
Highbury & Islington			WAGN GN Electrics Line and services to Hertford North and Welwyn Garden City Silverlink North London Line
King's Cross St. Pancras		Northern Line (Bank branch) Piccadilly Line Circle Line Metropolitan Line Hammersmith And City Line	WAGN services to Hertford North, Welwyn Garden City and Stevenage GNER East Coast Main Line
Euston		Northern Line	[Silverlink Watford Line]? and services to Birmingham Virgin Trains Intercity services
Warren Street		Northern Line (Charing + branch)
Oxford Circus		Bakerloo Line Central Line
Green Park		Piccadilly Line Jubilee Line
Victoria		Circle Line District Line	South East Trains South Coast Trains
Pimlico
[Vauxhall]?			South West Trains from Waterloo
[Stockwell]?		Northern Line
Brixton			South East Trains
south

The Victoria Line

Constructed in the 1960s, finished in the '70s; lovely light blue colour, and operating entirely underground. First tube line to have automatic operation. Not quite as shiny as it once was, but still damned fast and boasts a disproportionate number of connections.

Line guide: http://www.davros.org/rail/culg/victoria.html

Rolling stock: http://metadyne.tripod.com/1967tubeStock.html

History and timetables: http://www.thetube.com/content/faq/lines/Victoria.asp