1. Save Excel files into text
Saving Excel files into CSV can be done directly from Excel or through some external tools that allows batch operations. Native R functions for text data import can so be used.
2. Copy and paste from Excel to R
This is a fast solutions, but it has one main drawbacks: it requires to open Excel file, select data and copy. By the way, this is the best compromise when you're in a hurry.
3. ODBC connection
4. gdata package
5. xlsReadWrite package
6. XLConnect package
7.xlsx package