Here is Keith R.A. DeCandido, author of Supernatural: Nevermore and Supernatural: Bone Key, tentative appearances schedule for the next few months:
May
22nd-25th–Balticon 43 in Hunt Valley.
June
19th-21st–Heroes Convention in Charlotte, North Carolina.
July
10th-12th–Shore Leave 31 in Hunt Valley, Maryland.
23rd-26th–Comic-Con International in San Diego, California.
August
6th-10th–Anticipation, the 67th Annual WorldCon in Montréal, Quebec.
21st-23rd–4Pi-Con in Enfield, Connecticut.
September
4th-7th–Dragon*Con 2009 in Atlanta, Georgia.
18th-20th–FenCon VI in Dallas/Fort Worth,Texas.
November
20th-22nd–PhilCon 2009 in Cherry Hill, New Jersey
Source: Keith R.A. DeCandido LiveJournal.