I took Europe, social, and economy and tried to find the main points under those headings, not always an easy task... Of course, there's more to the candidates' programmes, positions, and history than I have put down, so please add in comments whatever you feel is missing.

I added appreciations like "ecology" or "productivism" under the "economy" heading, since that's definitely an important distinction to make on the French left, imo.

I've ordered the candidates roughly from left to right according to my lights.

• Arlette Laguiller (Lutte Ouvrière)
  
  Europe: for a united Europe once capitalism has been defeated; referendum non; constitution vague

  social: immediate €300 rise on all salaries and pensions; improve health, education, and pensions; nationalise housing, massive building programme

  economy: state control; productivism

• Gérard Schivardi (soutenu par le Parti des Travailleurs)
  
  Europe: anti-EU; referendum non; pro-withdrawal

  social: rural France, villages, public service (Post Office and school in every village)

  economy: anything but liberal

• Olivier Besancenot (Ligue Communiste Révolutionnaire)
  
  Europe: anti-EU as is; referendum non; constitution total rewrite by constituant assembly then referendum in each country

  social: increase social safety net, make the bosses pay, raise taxes

  economy: "anti-liberal"; public-sector, lip-service to ecology

• Marie-George Buffet (PCF)
  
  Europe: anti-EU as is; referendum non; constitution total re-founding of EU

  social: raise wages, pensions, increase social safety-net rights; public service for housing; increase state and public sector; raise taxes, cut loopholes

  economy: "anti-liberal"; public sector, productivist

• José Bové (29 May Collective)

  Europe: anti-EU as is; referendum non; constitution total re-founding of EU

  social: guarantee jobs, increase workers' rights, raise wages; seek gender equality; develop public services (inc. housing); promote sustainable development

  economy: "anti-liberal"; ecology/internationalism

• Dominique Voynet (Verts)

  Europe: pro-EU; referendum, oui; constitution, redefining the objectives of the EU (in English), newly-elected EP to write a constitution

  social: concept of social usefulness, ecological sustainability; so tax to be progressive and anti-pollution; raise minimum wage; all activity to be taken into account and given financial support, not just salaried work; promotion of social, co-operative/mutual, etc organisations

  economy: social democrat, ecology, some protectionism

• Ségolène Royal (PS)
  
  Europe: pro-EU; referendum, oui; constitution, rewrite followed by new referendum

  social: negotiated reform without social regression; maintain social protection, increase minimum wage; participative democracy; no sweeping tax changes

  economy: social democrat; ecology

• François Bayrou (UDF)
  
  Europe: pro-EU, (federalist), referendum yes. Constitution: negotiate a new treaty including institutional changes embodied in the first, submit to new referendum.

  social: maintain social safety net; maintain taxation level; weaken 35-hour week; allow new payroll-tax-free jobs, two per business; pay unemployed to work on community-useful jobs.

  economy: liberal

• Nicolas Sarkozy de Nagy-Bocsa (UMP)
  
  Europe: pro-EU as single market (but is not against political intervention eg ECB); referendum oui; constitution, wants a mini-treaty Merkel-style, ratified by parliament.

  social: restrain immigration, law'n'order, weaken 35-hour week and labour-market guarantees, weaken social safety net, replace only one out of two retiring civil servants, reduce taxes (50% tax ceiling), "create a new generation of family capitalists"

  economy: liberal (but dirigiste when it suits him)

• Frédéric Nihous (Chasse, pêche, nature, traditions)
  
  Europe: anti-EU; referendum non; constitution, no thanks (but in favour of EU reform, not withdrawal)

  social: rural France, villages, public service + traditional rights (shotguns and cheese in every village)

  economy: what?

• Philippe Le Jolis de Villiers de Saintignon (Mouvement pour la France)
  
  Copy/paste Jean-Marie Le Pen; add Catholic-aristocratic-rural into the mix; take out some, but only some, tax reduction.

• Jean-Marie Le Pen (Front national)
  
  Europe: sovereignist Europhobe; referendum non; constitution burn it

  social: foreigners out, social net for French only, suppress income tax, reduce company and wealth tax, increase VAT, privatize retirement pensions, double defence budget, women stay home have children

  economy: ultra-liberal, protectionist

You could regroup on the left by putting the three Trotskyite movements together: Schivardi, Laguiller, Besancenot. But, of these, only Besancenot gets the "anti-liberal" tag that comes from the movement (after the referendum on the EU constitution) that gave itself that name and attempted to field a single candidate, in vain. The three "anti-liberal" candidates, in that sense, are Besancenot, Buffet, and Bové. However, Bové could conveniently be grouped with Voynet as having genuine ecological concerns.