Here are the links to all the versions of the btsredist cab files.

UPDATE: JULY 2010. These Links are the working links.

CAB Files (32-Bit Editions)
The following table provides the locations of the localized CAB files for BizTalk Server 2009 running on 32-bit Windows.

Language        Link
CN      http://go.microsoft.com/fwlink/?LinkId=138895&clcid=0x804
DE      http://go.microsoft.com/fwlink/?LinkId=138887&clcid=0x407
EN      http://go.microsoft.com/fwlink/?LinkId=137254
ES      http://go.microsoft.com/fwlink/?LinkId=138889&clcid=0x40a
FR      http://go.microsoft.com/fwlink/?LinkId=138953&clcid=0x40c
IT      http://go.microsoft.com/fwlink/?LinkId=138891&clcid=0x410
JA      http://go.microsoft.com/fwlink/?LinkId=138900&clcid=0x411
KO      http://go.microsoft.com/fwlink/?LinkId=138965&clcid=0x412
TW      http://go.microsoft.com/fwlink/?LinkId=138898&clcid=0x404

CAB Files (64-Bit Editions)
The following table provides the locations of the localized CAB files for BizTalk Server 2009 running on 64-bit editions of Windows.

Language        Link
CN      http://go.microsoft.com/fwlink/?LinkId=138932&clcid=0x804
DE      http://go.microsoft.com/fwlink/?LinkId=138914&clcid=0x407
EN      http://go.microsoft.com/fwlink/?LinkId=137261
ES      http://go.microsoft.com/fwlink/?LinkId=138931&clcid=0x40a
FR      http://go.microsoft.com/fwlink/?LinkId=138956&clcid=0x40c
IT      http://go.microsoft.com/fwlink/?LinkId=138962&clcid=0x410
JA      http://go.microsoft.com/fwlink/?LinkId=138925&clcid=0x411
KO      http://go.microsoft.com/fwlink/?LinkId=138968&clcid=0x412
TW      http://go.microsoft.com/fwlink/?LinkId=138933&clcid=0x404