I'm also among the ranks of the spreadsheet-obsessed.
My main sheet has all of my positions listed, with 5 main groups: General Equity, Conservative Income (REIT/Utilities), Int'l, Natural Resources, and Fixed Income. I simply download .csv files from Yahoo each week and copy and paste the price columns into my spreadsheet categories to see the current values each week, and then record the NAV for each account to track its fluctuation.
Of course, one of the more critical elements of my spreadsheet is to list the dividend in one of the columns, and compute the yields off of my basis and current price. I then have a total income for each account (based on dividends, not cap gains) to see what my 'recurring' annual income is, and also track that number (I look at each holding twice a year to update the current annualized dividend, and note with different colors if it's increasing or decreasing, along with the previous dividend, so I can track the growth/decline of each holding's dividend at a glance).