Specifically from this list: http://www.ebay.in/sch/i.html?_from=R40&_sacat=0&_nkw=speaker%20usb&_sop=15
X-mini is quite a good speaker, portable and rechargeable and the sound is satisfactory.
Of that particular list, the Philips, Creative and Logitech would be at the top of the list.
I can also vouch from experience that the "Laptop Speaker 5 Watt Multi Media USB Powered" (or at least one that looks just like it) is well built and has decent sound. It is, however, only USB _powered_ and uses analogue input for the actual sound.
Bear in mind that at this price level you are not going to get the best sound in the world, and you get what you pay for. Also, a larger loudspeaker will give you better base than a small one (again, at these price levels and speaker size). Personally, I'd go with the Philips.
Sounds v.honest suggestion
Go for Creative :)
If you are looking for cheap priced decent quality speakers, Logitech is good, the Z series are quite good. It really depends on what you are wanting the speakers for and what to expect. General purpose use, these speakers are fine. For better quality, Creative would be a better choice at a fair price.
Appending a sub-question : Does using usb connection for speaker reduce the sound than if it were connected directly through pin-socket?
( usb is an extension and so the sound reduces? )
The clarity might not be as good through the USB connection as it would through the 3.5mm audio jack, but I don't think the noticeable difference is by much if you get decent quality speakers.
Sony and Creative are high quality brands you can look for. Filter the results to see their speakers and read their reviews from different websites.
you have few choices
Edifier M1250 USB
Logitech Z110 USB Stereo Speakers
HP Compact 2.0 Speakers Portable Size MINI USB-Powered
zebronics looks fine they have web page