I'm a geek: I keep a spreadsheet.
I have the different links along the top columns, sorted by type of challenge (card, LO, other) and then by the day of the week that they start. I have the dates down the side, and I colour in the blocks of days that each challenge runs for. I have today's date showing in red so that I can see instantly when I'm nearing the end of the challenge. When I complete each one, I change the colour and add my entry on the date so I can see which I have left to do. I also copy any photo inspirations into it.
Then I can print off the current challenges and take the sheet to a crop. I don't enter every challenge every time, but it gives me a great choice of inspiration to choose from. It works for me.