Uget

Have you thought about adding Metalink support? It's an XML file that lists
mirrors & checksums.

http://en.wikipedia.org/wiki/Metalink

Many Linux distros, OpenOffice.org, & other projects use it. Most download
managers support it, including mulk ( http://mulk.sourceforge.net/ ) which
is also written in C & based on libcurl.

<?xml version="1.0" encoding="UTF-8"?>
<metalink version="3.0" xmlns="http://www.metalinker.org">
<files>
<file name="example.ext">
<verification>
<hash type="md5">example-md5-hash</hash>
<hash type="sha1">example-sha1-hash</hash>
<signature type="pgp"/>
</verification>
<resources>
<url type="ftp" location="us"
preference="90">ftp://ftp.example.com/example.ext</url>
<url type="ftp" location="uk"
preference="90">ftp://ftp.example.net/example.ext</url>
<url type="http" location="us"
preference="90">http://example.com/example.ext</url>
<url type="http" location="de"
preference="90">http://example.net/example.ext</url>
</resources>
</file>
</files>
</metalink>