Since there will be a few new owners of this phone in the next little bit. I figure I'd post something on the accessories.
If you need a basic screen protector I have like 4 or 5 of them I can really just give away. Otherwise I'd strongly recommend a tempered glass screen protector. They are a bit pricey, but well worth the price. My friend dropped her OnePlus and the screen protector shattered but not her screen. Orzly makes probably the best one followed by Godosmith. Nillkin is good too, but there are a lot of fake ones around, but the cutouts and coating are not as good
Orzly Tempered Glass $16.99 (expensive but great, north american shipping)
http://www.amazon.ca/Orzly%C2%AE-Tem...=orzly+oneplus
Godosmith ($10 but slow shipping from China)
http://www.aliexpress.com/item/Origi...909867131.html
Normal screen protectors
EZ guard 6 pack ($1 for traditional screen protector)
http://www.amazon.ca/6-Pack-EZGuardZ...reen+protector
For cases and accessories Aliexpress probably has the best selection of cases since the phone has a huge following in China, but if you want just a basic case and not through oneplus themselves, diztronic makes very good TPU cases which is on sale right now.
http://www.amazon.com/Diztronic-Matt...tronic+oneplus
Bumpers are also somewhat good but there is debate whether this affects signal strength
http://www.aliexpress.com/item/Onepl...923284720.html
Community links for oneplus
Official
https://forums.oneplus.net
Reddit
http://www.reddit.com/r/oneplus/
XDA:
http://forum.xda-developers.com/oneplus-one