If you want a USB mic then the Rode Podcaster is a good choice. If you're wanting to go XLR and buy pre amps and converters then I'd suggest the Heil PR-40 or the Rode Procaster. Either way make sure you get a boom and a shock mount for them.
I would get a usb combo mic/speaker combination that has echo cancellation. Something like the IPEVO X1-N6 or the PHOENIX AUDIO PCS MT202/PCO Duet VoIP Speakerphone