[OT?] ETL tools

Hi there,

I have started working on a new place where they have a lot of medical
data stored in relational databases they later exploit with
statistical software. The situation is a bit chaotic as they're using
a lot of local Access databases, some databases hosted in an old
version of Microsoft SQL Server and a lot of data in other non
relational files (SPSS, Excel, ...). I was hoping to impose a bit of
order and I started installing a current version of PostgreSQL to host
all the databases they're using.

I now have two problems:

1. I have to migrate all the data they currently have to the new
system, maybe making some transformations in the way.

2. They're continously receiving new data in heterogeneous formats and
I need some way to import this data in a easy way into the existing
databases.

Googling a bit I have discovered that what I probably need is an ETL
(extract, transform and load) tool, preferably open sourced and very
PostgreSQL friendly... does anybody on this list have experience with
such kind of tools? Would anybody recommend anything? Maybe I could
try another approach?

Thanks in advance, best regards
Jose