Each person non resident of the Russian Federation prior to applying for visa in the consulate must get an invitation according to the purpose of his or her visit.
Your Visa To Russia provides invitations for tourist and business trips.

The kremlinologist catechism

There is a catechism that dominates American discourse on Russia today, any many of its underlying assumptions are unsupported by facts, figures or statistics.

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Source: http://www.russianlife.com/article.cfm?Number=2087