Rails to MySQL data types

MySQL Column Data Type to Ruby class type (when using ActiveRecord)

MySQL Data Type	Empty Ruby Class	Ruby Class
bigint	NilClass	Bignum
binary	String	String
blob	String	String
bool	NilClass	TrueClass FalseClass
char	String	String
date	NilClass	Date
datetime	NilClass	Time
decimal	NilClass	Fixnum
double	NilClass	Float
enum	String	String
float	NilClass	Float
int	NilClass	Bignum
longblob	String	String
longtext	String	String
mediumblob	String	String
mediumint	NilClass	Fixnum
mediumtext	String	String
set	NilClass	String
smallint	NilClass	Fixnum
text	String	String
time	NilClass	Time
timestamp	NilClass	Time
tinyblob	String	String
tinyint	NilClass	Fixnum
tinyint(1)	NilClass	TrueClass FalseClass
tinytext	String	String
varbinary	String	String
varchar	String	String
year	NilClass	String

For completeness sake, here's a summary of Rails migration types and their MySQL column data types.
Rails Migration Type to MySQL Column Data Type

Rails Migration Symbol	MySQL Data Type
:binary	blob
:boolean	tinyint(1)
:date	date
:datetime	datetime
:decimal	decimal
:float	float
:integer	int(11)
:string	varchar(255)
:text	text
:time	time
:timestamp	datetime

gem development/packaging ref

gem development reference

http://sirupsen.com/create-your-first-ruby-gem-and-release-it-to-gemcutter/
http://integrumtech.com/2010/01/how-to-build-a-ruby-gem/