I write them off, they appear on my CC statements so I just make a note beside them as to what they are for.
I ask for receipts for pretty much every purchase. Most are willing to send a quick .doc that's fine as a receipt.
I claim those and everything else in the field. I try to use PayPal as close to 100% of the time as possible, makes for neat accounting.
Always ask for a receipt. There's no reason the taxman should have your money, just because you haven't gathered the right paperwork.
Even without a receipt you should have some kind of documentation... a paypal invoice (or your own record of what you paid out), an email discussing the transaction, etc. Get a receipt when you can... but at least make sure you have something any time you're paying money out.
Yes they are definitely legit business expenses, but I can't believe that a line item in my PayPal for $30 to some email address is really good enough for the IRS. But hey, if everyone else is doing it...
You should be using the invoicing function there to keep better records, and always at least use the note field, so the reason for the charge/payment is documented in some way.