Mirrors/P2P & checksum in one link
 

Metalink could be a nice feature for LimeWire.

Metalink bundles the various ways (FTP/HTTP/P2P) to acquire a file into one format for easy content distribution. It currently supports BitTorrent, ed2k, & magnet links but can be easily extended to support other P2P methods.

Currently, GetRight, aria2, and Speed Download support Metalink 3.0, but other download managers are adding support...

http://www.metalinker.org/

There's also a video at There's a video of metalink working in GetRight here: http://www.metalinker.org/implementation.html

They look like this:

<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>
</verification>
<resources>
<url type=”ftp”>ftp://ftp.example1.com/example.ext</url>
<url type=”ftp”>ftp://ftp.example2.com/example.ext</url>
<url type=”http”>http://www.example1.com/example.ext</url>
<url type=”http”>http://www.example2.com/example.ext</url>
<url type=”http”>http://www.example3.com/example.ext</url>
<url type=”bittorrent">http://www.ex.com/example.ext.torrent</url>
<url type=”magnet”/>
<url type=”ed2k”/>
</resources>
</file>
</files>
</metalink>

Features
Backward compatible with regular hyperlinks.
Combines FTP and HTTP with Peer-to-peer (P2P, shared bandwidth).
No Single Point of Failure (SPOF) like FTP or HTTP URLs. More fault tolerant.
Standard unified format that collects links for automatic accelerated (segmented) downloads from multiple sources.
Automatic load balancing distributes traffic so individual servers are under less strain.
Useful for automatic updating programs when new versions are released.
No long confusing list of possibly outdated Mirrors and P2P links.
Makes the download process simpler for users (automatic selection of language, Operating System, location, etc).
Stores more descriptive and useful information for software distribution.
No separate MD5/SHA-1 file or manual process for verification.
Uniquely identifies files, so even if all references to it in the Metalink stop working, the same exact file can be found via a P2P or Web search.
Can finish P2P downloads even if no full seeds are shared.
For FTP/HTTP, an updated client is needed, but not a separate client like some types of P2P.

There's a new cross platform metalink client: wxDownload Fast.

OpenOffice.org uses metalink to distribute their free office suite. Some Linux distributions are using it now too.

It would be cool if .metalink file reading could be added to LimeWire.

Speed Download is a new Mac metalink client.

Here's a good explanation of metalink too:

'Metalink makes complex download pages obsolete by replacing long lists of download mirrors and BitTorrent trackers with a single .metalink file. As you might have already guessed, a .metalink file is a file that tells a download manager all the different ways it can download a file. The file itself takes the form of an open XML standard that can list an unlimited number of HTTP and FTP sources as well as BitTorrent trackers and ed2k and magnet links.'
(http://www.downloadsquad.com/2006/08...ftp-downloads/)