Most of the organizations on Lotus Notes looking to migrate to SharePoint due to the operation cost and maintenance of their existing Lotus Notes Applications.  The migration process needs to go through a methodical analysis of existing applications' business value, based on which it needs to be migrated/rebuilt to SharePoint.  But just to get a quick idea on how Lotus Notes artifacts can be re-written to SharePoint equivalent items:

  1. Lotus Notes Database = SharePoint Lists
  2. Views = SharePoint List View
  3. Forms = SharePoint List Forms / InfoPath Forms
  4. Lotus Notes Scripts/Agents = C# code-behind

For data migration, there are lot of third-party tools available to read it from Lotus Notes DB to SharePoint lists.  The most commonly used and efficiently used one is CASAHL.  Before doing the data migration, the source data in Lotus Notes DB should be cleansed thoroughly and ensure data consistency to match the target SharePoint list schema, as Lotus Notes DB manage data in well-defined schema.  Another thing to remember is, since Lotus Notes is a thick client application, for a geographically distributed organizations, the users might have entered data in different time zone & currency values for the same DB column.  Just a quick pointers before you start thinking of migrating....