Parse the ConnectionString information out of SSIS packages stored in MSDB on 2008/R2/2012. SSISDB will have to be handled differently.

gistfile1.sql

DECLARE	@DTS_Packages TABLE
	(
	PackageName SYSNAME,
	PackageDescription SYSNAME,
	Creator SYSNAME,
	CreateDate DATETIME,
	PackageXML XML
	)

INSERT	INTO @DTS_Packages
SELECT	p.[name] AS [PackageName],
	[description] AS [PackageDescription],
	l.[name] AS [Creator],
	p.[createdate],
	CAST(CAST(packagedata AS VARBINARY(MAX)) AS XML) PackageXML
FROM	[msdb].[dbo].[sysssispackages] p
JOIN 	sys.syslogins l
	ON p.[ownersid] = l.[sid];
--you either need ;WITH or the previous statement needs the semicolon for the
--WITH NAMESPACE... which precludes a CTE
WITH XMLNAMESPACES ('www.microsoft.com/SqlServer/Dts' AS dts) 
SELECT [@DTS_Packages].PackageName,
	[@DTS_Packages].PackageDescription,
	[@DTS_Packages].Creator,
	[@DTS_Packages].CreateDate,
	[@DTS_Packages].PackageXML, 
	Con.Str.value('.', 'varchar(500)') --aka give me that exact node
FROM @DTS_Packages
CROSS APPLY PackageXML.nodes('//dts:Property[@dts:Name="ConnectionString"]') AS Con(Str)