limewire addons
 

are there any programs or application available that can improve the download effectiveness of limewire ?

There are download accelerators around but they're a waste of time, so please don't be sucked in by them;)
accelaration patch
No more internet (not just LimeWire) thanks to Accelerator
2 easy questions for you smart folks
LimeWire Accelerator Patch?

Have a look at the thread below (the first few posts by murasame) for tips to optimise LW's performance.
A few things to consider while configuring Limewire for optimal performance...

Some ISPs will throttle bandwidth for p2p, if you think that your download speeds are really way too slow, post back & tell us who your ISP is.
You can do a speed test here & tell us the results.
Speedtest.net - The Global Broadband Speed Test

And also download a file from here & tell us what kind of download speed you see.
Magnetmix