You might as well watch them in production/publish order:

1. Hidamary Sketch
2. Hidamari Sketch (special)
3. Hidamari Sketch × 365 (TV)
4. Hidamari Sketch × 365 (special)
5. Hidamari Sketch × Hoshimittsu (TV)
6. Hidamari Sketch × Hoshimittsu (special)
7. Hidamari Sketch × SP (special)
8. Hidamari Sketch × Honeycomb (TV) (sequel)
9. Hidamari Sketch: Sae/Hiro Sotsugyō-hen (OAV)

(listing from ANN's page.  Hulu has everything except the last OAV - the specials are part of the previous main season)

The problem is that episodes aren't completely in chronological order. There's two groups:

• Hidamari Sketch + Hidamari Sketch × 365 (Yuno & Miyako year 1)
• × Hoshimittsu + × SP + × Honeycomb + Sae/Hiro Sotsugyō-hen (Yuno & Miyako year 2)

Episodes in the first groups are less ordered. Episodes in the second group are more in order, but also have some episodes that chronologically take place during the first group.

You might as well watch them in production/publishing order:

1. Hidamari Sketch
2. Hidamari Sketch (special)
3. Hidamari Sketch × 365 (TV)
4. Hidamari Sketch × 365 (special)
5. Hidamari Sketch × Hoshimittsu (TV)
6. Hidamari Sketch × Hoshimittsu (special)
7. Hidamari Sketch × SP (special)
8. Hidamari Sketch × Honeycomb (TV) (sequel)
9. Hidamari Sketch: Sae/Hiro Sotsugyō-hen (OAV)

(listing from ANN's page. Everything except the last OAV is on Hulu - the specials are part of the previous main season)

The problem is that episodes aren't completely in chronological order. There're two groups:

• Hidamari Sketch + Hidamari Sketch × 365 (Yuno & Miyako year 1)
• × Hoshimittsu + × SP + × Honeycomb + Sae/Hiro Sotsugyō-hen (Yuno & Miyako year 2)

Episodes in the first groups are less ordered. Episodes in the second group are more in order, but also have some episodes that chronologically take place during the first group.