so so far i have been using my arduino to program small atmel chips, but im in need of something much larger with more pwm channels.

i'm looking for some kind of interface that i can hook up a variety of atmel chips and program them so they run the arduino sketches.

i wanted to use a atmega48 chip but can't seem to get the boards entry so apparently need a standalone usb device to program it that allows me to use my arduino sketches

 

What is probably the best all-around AVR programmer is Atmel's AVRSIP2, which connects directly via USB. Its $37 at Digikey, its integrated with AVR Studio and supports (I think) all of the ATMEGA and ATTINY parts. I suggest staying away from the imitations.
http://www.digikey.com/

If a command line operated programmer is your preference, you should have a look at USBasp programmers. You can built it yourself, or you can buy it from many places, such as Digikey or DealExtreme for about $10 ±$5 including shipping. They are not branded. I still recommend the AVR ISP.

http://dx.com/p/51-avr-programmer-isp-download-usb-asp-downloader-148855

You might also want to have a look at USBtinyISP, which also works with AVRStudio and AVRDude
http://www.ladyada.net/make/usbtinyisp/