The Wikitravel (.org) and Wikivoyage (.org) ( WMF competitor to Wikitravel ) contain a wealth of information on travelling ecologically on mass transit nearly anywhere and provide a wealth of knowledge from both local and traveler wealth of knowledge.

A journey planner (or trip planner) is a specialised electronic search engine used to find the best journey between two points by some means of transport. ( Wikipedia )

An Intermodal Journey Planner (IJP), or Trip Planner is computer system which can provide a traveller with an itinerary for an intermodal passenger transport journey. The system can provide timetable, routing and other travel information. A single journey may use a sequence of several modes of transport, meaning that the system must know about public transport services (bus, train, aeroplane, tram, metro) and about transportation networks (roads, footpaths, cycle routes) for private transportation (automobile, walking, bicycle). ( Wikipedia )
A public transport route planner is a type of journey planner designed to provide information about available public transport journeys ( Wikipedia )
Intermodal passenger transport, also called mixed-mode commuting, involves using two or more modes of transportation in a journey. ( Wikipedia )

The journey planners are listed by country or area of service, countries are sorted under languages. ( Wikipedia )

Here are the ones with most coverage / utility

http://www.rome2rio.com/ - w:Rome2rio is a worldwide multimodal transport search engine that displays realistic prices. This site seems to work fairly well. The prices it gives are slightly inflated from what you would as a local expect to get it for but they are hitting the mark on what a tourist will pay for booked-on-the-go ticket. No direct booking.

Google Transit a multi-modal journey planner for US and also serves areas in Africa, Australia, Europe and India ( w:International availability of Google Transit )

The coverage of Google Transit is publicly available. It is spread worldwide, in hundreds of cities and sometimes in entire countries such as China, Japan, Switzerland. The coverage of major cities in the United States and in Canada is almost exhaustive. In some areas (North East, North West, South West, Wales, West Midlands and Yorkshire) of the United Kingdom, Google Transit covers only part of the transit agencies. In other areas, Google Transit does not provide public transit directions, but still provides the Transit Layer which overlays the schematic of the transit lines on the map. Notable examples include Paris, Berlin, Mexico City and many other capitals around the world. ( Wikipedia)

Europe-wide multi-modal mass transit journey planner by Deutch Bahn with ability to purchase tickets for travel within Germany

Shared transport is a term for describing a demand-driven vehicle-sharing arrangement, in which travelers share a vehicle either simultaneously (e.g. ride-sharing) or over time (e.g. carsharing or bike sharing), and in the process share the cost of the journey, thereby creating a hybrid between private vehicle use and mass or public transport. [...] ( Wikipedia )

Shared transport modes

Bicycle sharing system
Demand responsive transport
Real-time ridesharing
Flexible Carpooling
Green travel
Hail and ride
High-occupancy vehicle lanes
Hitchhiking
Paratransit
Public space
Remote Office Centers
Ride-sharing
Share taxi
Slugging
Sustainable transport
The commons
Vanpooling
Carsharing or car sharing (US) or car clubs (UK) is a model of car rental where people rent cars for short periods of time, often by the hour. ( Wikipedia )
Carpooling (also car-sharing, ride-sharing, lift-sharing and covoiturage), is the sharing of car journeys so that more than one person travels in a car. ( Wikipedia )

DMOZ.org list of carpooling schemes

Real-time ridesharing (also known as instant ridesharing, dynamic ridesharing, ad-hoc ridesharing, on-demand ridesharing, dynamic carpooling, and provided by transportation network companies) is a service that arranges one-time shared rides on very short notice. ( Wikipedia )

A transportation network company (TNC) is a company that uses an online-enabled platform to connect passengers with drivers using their personal, non-commercial, vehicles. This can be considered a type of ridesharing. Examples include

Lyft
Uber X
Sidecar
Wingz
Summon
Haxi. ( Wikipedia )

When traveling alternative check out some review aggregators to find good places to eat, stay, enjoy, experience.

This is a list of information services that allow you to access shared and alternative transport and journey planners.

English

North America

http://www.busbud.com/ - Busbud is a world-wide bus and coach travel company that enables travellers to easily search, compare, and book their intercity bus tickets. ( Wikipedia )

Busbud cannot find any connections from Helsinki to Saint Petersburg ( as of January 2015 ) even though in reality there are ample connections between the cities.

UK

Journey planners for UK

Rail journey planner by National Rail for UK
Brighton & Howe journey planner
Multi-modal journey planner for the greater London area ( also walking and biking journey planner )
Transport for Greater Manchester multi-modal journey planner

Carpooling in UK

http://www.blablacar.com/ - a w:carpooling or ride sharing service connecting passangers looking for reasonably priced travel from place to place with drivers looking for company to pass the time and someone to pick up the gasoline bill

Carsharing services in UK

Australia

Carpooling in Australia

Carpoolone.com.au free carpooling for Australia

Carsharing services in Australia

GreenShareCar
Car Next Door
GoGet

Canada

Carsharing services in Canada

AutoShare
Calgary Carshare
Car2Go
CarShare HFX
CarShare NL
Coast Car Co-op
Communauto
Community CarShare,
Kootenay CarShare
Modo The Car Co-op
Okanagan CarShare
Options For Cars
Peg City Car Coop
Regina CarShare, Saskatoon CarShare
Victoria CarShare
Zipcar

India

Carsharing services in India

ZoomCar

Ireland

Carsharing services in Ireland

GoCar

New Zealand

Carsharing services in New Zealand

United states

Carsharing services in USA

Belgium

Carsharing services in Belgium

Czech / Czech Republic

Multi-modal and local journey planners in Czech Republic

http://www.portal.idos.cz/

Carsharing services in Czech Republic

AJO.cz

Estonian / Estonia / Eesti

Multi-modal and local journey planners in Estonia

Peatus.ee journey planner covering whole Estonia

Finnish / Finland

Multi-modal and local journey planners in Finland

Matka.fi - mass transit multi-modal journey planner for whole Finland by the Finnish Transportation Agency

Journey planner for greater metropolitan area of Helsinki (Helsinki, Espoo, Vantaa, Kauniainen, Kerava, Kirkkonummi, Sipoo)- 1st of it's kind in Finland