Hilarious in Hindsight: Enrico asks "[[ Wait, is that Integra's team getting completely demolished?]]" That very day England gets trounced by Germany 4-1, getting eliminated from the 2010 World Cup. (It counts cause the comic went up at midnight EST Sunday, hours before the game began.)
Schedule Slip: Oddly enough, when this happens, it's usually because something is up with the host site. When Erin needs a break for schoolwork or her computer being on the fritz (again), she posts guest comics, and more recently a feature on Integra fansites.
Though there was one time she deliberately postponed the plot for more Integra spottings: she felt uncomfortable posting a story about a fictional London burning at the same time as the real life London riots were happening.
Madeline and Friends: Madeline's adventures in the Holy League. Never got past a cast of characters (Madeline, Pepito, and a Muslim girl codenamed Mitraille).
Catholintegra: Enrico finds an I-Jin of Gregor Mendel and tries to create a Catholic version of Integra. Dropped cause Caterina Sforza of Trinity Blood made a good Catholic Integra already, so it was retconned into an Iscariot in the far future being more successful in creating Catholintegra than Enrico was.
Let The Flames Begin: A Mirror Universe where instead of fangirls invading, flamers do.
A Proper Lupin III Adventure: Hellsing is recruited to stop Lupin III from stealing the Crown Jewels.
Hellsing Heir Auditions: Integra seeks out someone to adopt as her heir. Dropped when the Grand Finale of Hellsing reveals that the head of Hellsing will be a government-appointed position from now on, starting with Penwood's grandson.