In google adwords I notice that there is a delay of at least two days before conversions are reported, but the rest of the data (clicks, cost, ctr, etc) shows up almost real-time. Is there any documentation that specifies a standard for why or how long it takes for conversions to show up on the adwords interface?
The click and the recorded conversion needn't happen at the same time. Google track conversions for up to 30 days after the click (http://adwords.google.com/support/aw/bin/answer.py?hl=en&answer=86282). Whilst the help text doesn't say why there's a delay I would guess that given that the two things can be separated by time they are waiting until there's a couple of days of statistics to give you. As that page says, the conversions are counted on the day the click occurs, not the conversion, so if you rerun the report later the figures for a given day may go up.
I'm pretty sure while studying for the adwords exam it mentions the cookie file stays present for up to 30 days, so the conversion can take place up to 30 days after the click actually occurred.