Catflip: Parameters - https://catflip.co/ Shows the current values for each of the major system parameters. This includes the more commonly known parameeters, such as stability fees for each collateral package, and the less commonly known parameters, such as those related to auctions, accounting and the GSM.
DAI Stats - https://daistats.com/ Shows an overview of the current state of the Maker Protocol. Including total DAI minted against each collateral type, current Stability Fee and DSR settings, and the current system surplus / debt.
MakerBurn - https://makerburn.com/ Clean and Elegant UI. Shows current and historical DAI supply, amount of DAI locked in the DSR, annual MKR token burn rate and highlights any recent changes.
DAI.Stablecoin.Science - https://dai.stablecoin.science/ Provides data and a basic graphs showing the DAI price from recent DAI/ETH trades on leading DEXs and CEXs.
DAI Peg - https://daipeg.com/ Takes dai.stablecoin.science data and divides it by trading venue. Allows filtering by trade size and gives a Daily Weighted average of the DAI price based on these trades.
Descipher.io: DAI - http://dai.descipher.io/ Sources data from DAI.stablecoin.science and uses it to display Volume Weighted Average graphs of the DAI price over various time windows. Gives a good single look visual understanding of where DAI is trading in relation to the peg, and which exchanges are seeing the most DAI/ETH volume.
DeFi.ai: DAI - https://defi.ai/dai Shows how much DAI can be bought or sold on coinbase or Radar Relay above or below the $1 peg. Gives a visual representation of the orderbook on coinbase.
Descipher.io: MakerVaults - http://makervaults.descipher.io/ Shows the current spread of vaults and their liquidation prices on each collateral type. Also shows the various spread of collateralization ratios across vaults. Incredibly useful for finding out what impact a market dip will have on the Maker Protocol, how much DAI will be liquidated, and identifying any 'danger zones' at which point large amounts of DAI would be liquidated.
DeFI Explore: Liquidations - https://defiexplore.com/liquidations Shows all active and finished liquidations across all collateral types. Shows the current and final status of each liquidation and detailed information about individual lidquidations can be veiwed. Useful if you are searching for an individual liquidation, or if you want to see the general outcome of a certain set of liquidations.
Twitter: MakerDaiBot - https://twitter.com/MakerDaiBot Tweets a number of useful bits of information about the Maker Protocol, including large mints/burns, parameter changes, and 24-hour summaries. Useful if you want up-to-the-minute information of any significant changes in the Maker Protocol.
Santiment: Maker Overview - https://graphs.santiment.net/makerdao#overview Shows an overview of DAI and the Maker Protocol. Useful as an 'at-a-glance' overview of what is going on.
Santiment: Maker Pro - https://graphs.santiment.net/makerdao-pro#mcd_stats Shows multiple in-depth and deep statistics regarding user behavior in the Maker Protocol. Useful if you want detailed, comparitive information about almost any aspect of the Maker Protocol. Particularly useful to see DAI token usage and aggregated social data.
MakerBurn: Rundown - https://makerburn.com/#/rundown Shows an 'at-a-glance' view of the current collateral packages and their current parameters. Also estimates the annual fees produced from each one given the current parameters. Useful for a simple view of the current state of collateral packages and which are earning the most income for the Protocol.
DAI Auctions - https://daiauctions.com/# Shows current auction parameters and the status of auctions that have triggered within the last few days. Useful to show how liquidations are going, and give a rough idea of keeper participation. Especially useful in emergency situations in which a large amount of DAI debt has been liquidated.
Catflip: Changelog - https://catflip.co/changelog Shows the previous and changed values for system parameters that have changed in each historical executive vote. Useful for figuring out when a certain parameter was last changed.
MKRGov.science - https://mkrgov.science/ Shows governance analytics for current and historical votes. Also shows aggregated data based on the outcome of individual votes. Useful to find out the outcome of a particular proposal or poll, and find out how many addresses voted in it, the distribution of MKR over time and options.