There are many USB/Serial adapters like the FTDI Basic, which uses an FTDI FT232 chip, you can find them with FT232RL package with leads, FT232RH with no leads, and various USB connectors (large USB-B, smaller USB-B Mini, and really small USB-B Micro).
You can find them with PL2303 chip instead, with CP2102 chip, WD403 (I think that's the number), showing up on numerous clones, and with Atmega8U2 at the Arduino store.
All three of those need an external crystal. The FT232 has in internal oscillator and needs no crystal.
FTDI had their driver not working with counterfeit FT232 chips for a while.
PL2303 I thought had driver troubles (or no driver available) with Win7 or Win8.1. You should check on that. I've only used FTDI based boards myself with Win7 Pro and IDE 1.0.6 as one reference point.
I did try some CP2102 modules when I was running WinVista a year+ ago, modified with a trace cut and jumper add to bring the DTR signal out to the IO pin (vs the chip's Reset signal). Those worked fine.